Array pointer in array

Can anybody tell me how to create pointers in an array pointing to other arrays?

RichL wrote:
Hi tbob,
thanks for your suggestion! I did build it up with three arrays and a numeric control to select one of the arrays, which works fine. However, there are the following effects which I don't understand yet.
1. The RefArray can only be defined as Variant, showing a violet colour instead of a green/blue as in your example; I could not find a refnumber without giving me an error.
2. By changing the array selector, following array elements are being written into: 1,1 of array0; 0,0 of array1 and 1,0 of array2. I don't see why it is different for each array. Is there a possibility to select the array element being written into?
My VI is attached, LV7.1
Kind regards
Richard
Strange, when I created my vi, the RefArray was blue-green, not a Variant. On the front panel I placed a blank array. Then I placed a Control Refnum into the array. Now the array is defined as a Control Refnum Array, not a Variant.
Attached is a vi similar to the picture I had previously attached. In your case, you would need a slightly different method because of your unknown quantities of channels for each source. The use would select a source, and then you would have to retrieve an array of channels for that source. The user then selects a channel, and you would have to retrieve the data for that channel.
Post what you have so far so that we can look at it.
- tbob
Inventor of the WORM Global
Attachments:
RefArray.vi ‏50 KB

Similar Messages

How to get data from a pointer to an array using dlportio?

I use DLPORTIO.DLL to access the parallel port on a WinXP. The purpose is to read data coming from an fpga.
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DLPORTIO.DLL can buffer data from the parallel port.
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Attachments:
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LabVIEW does not have a 128 bit numeric so you will need to create a work around of sorts. What I would suggest is creating some wrapper dll functions. These funcitons would take say an array of U8s from LabVIEW, convert them into your 128 bit number and then call your dll with that.
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How do I create a 1d array that takes a single calculation and insert the result into the first row and then the next calculation the next time the loop passes that point and puts the results in thsecond row and so on until the loop is exited.

The attached file is work inprogress, with some dummy data sp that I can test it out without having to connect to equipment.
The second tab is the one that I am having the problem with. the output array from the replace element appears to be starting at the index position of 1 rather than 0 but that is ok it is still show that the new data is placed in incrementing element locations. However the main array that I am trying to build that is suppose to take each new calculation and place it in the next index(row) does not ap
pear to be working or at least I am not getting any indication on the inidcator.
Basically what I am attempting to do is is gather some pulses from adevice for a minute, place the results for a calculation, so that it displays then do the same again the next minute, but put these result in the next row and so on until the specifiied time has expired and the loop exits. I need to have all results displayed and keep building the array(display until, the end of the test)Eventually I will have to include a min max section that displays the min and max values calculated, but that should be easy with the min max function.Actually I thought this should have been easy but, I gues I can not see the forest through the trees. Can any one help to slear this up for me.
Attachments:
regulation_tester_7_loops.vi ‏244 KB

I didn't really have time to dig in and understand your program in depth,
but I have a few tips for you that might things a bit easier:
- You use local variables excessively which really complicates things. Try
not to use them and it will make your life easier.
- If you flowchart the design (very similar to a dataflow diagram, keep in
mind!) you want to gather data, calculate a value from that data, store the
calculation in an array, and loop while the time is in a certain range. So
theres really not much need for a sequence as long as you get rid of the
local variables (sequences also complicate things)
- You loop again if timepassed+1 is still less than some constant. Rather
than messing with locals it seems so much easier to use a shiftregister (if
absolutely necessary) or in this case base it upon the number of iterations
of the loop. In this case it looks like "time passed" is the same thing as
the number of loop iterations, but I didn't check closely. There's an i
terminal in your whileloop to read for the number of iterations.
- After having simplified your design by eliminating unnecessary sequence
and local variables, you should be able to draw out the labview diagram.
Don't try to use the "insert into array" vis since theres no need. Each
iteration of your loop calculates a number which goes into the next position
of the array right? Pass your result outside the loop, and enable indexing
on the terminal so Labview automatically generates the array for you. If
your calculation is a function of previous data, then use a shift register
to keep previous values around.
I wish you luck. Post again if you have any questions. Without a more
detailed understanding of your task at hand it's kind of hard to post actual
code suggestions for you.
-joey
"nelsons" wrote in message
news:[email protected]...
> how do I create a 1d array that takes a single calculation and insert
> the result into the first row and then the next calculation the next
> time the loop passes that point and puts the results in thsecond row
> and so on until the loop is exited.
>
> The attached file is work inprogress, with some dummy data sp that I
> can test it out without having to connect to equipment.
> The second tab is the one that I am having the problem with. the
> output array from the replace element appears to be starting at the
> index position of 1 rather than 0 but that is ok it is still show that
> the new data is placed in incrementing element locations. However the
> main array that I am trying to build that is suppose to take each new
> calculation and place it in the next index(row) does not appear to be
> working or at least I am not getting any indication on the inidcator.
>
> Basically what I am attempting to do is is gather some pulses from
> adevice for a minute, place the results for a calculation, so that it
> displays then do the same again the next minute, but put these result
> in the next row and so on until the specifiied time has expired and
> the loop exits. I need to have all results displayed and keep building
> the array(display until, the end of the test)Eventually I will have to
> include a min max section that displays the min and max values
> calculated, but that should be easy with the min max function.Actually
> I thought this should have been easy but, I gues I can not see the
> forest through the trees. Can any one help to slear this up for me.

How can I convert these 250 data points in a spreadsheet file into an array???!!!

I want to convert these points(see spreadsheet file attached) into a 1-D array of numbers and plot them using a vi. I am using the readfromspreadsheet.vi and it just gives me a number 4 and plots that. Please tell me what to do...I'm confused and have a project due!!!
Attachments:
ec1.xls ‏14 KB
test.vi ‏14 KB

Save the excel spreadsheet as tab delimited text file and use "Read From Spreadsheet File" vi to read it.

How can I convert 400 data points from a spreadsheet file to an array?

The spreadsheet file contains over 5000 data points (in one column) of which I only want the first 400 and want to convert them to an array in Labview. I tried to use the 'readfromspreadsheet' vi but it wasn't much help. Please tell me how i should approach this problem and what vi's to use.

I attach a model vi that you can experiment with. You will need to know the formatting of the data in your file, from there -plus the delimiter- you'll be able to estimate how many characters makes the first 400 data point. It's possible to develop a more robust vi to do this, in the mean time, the attached vi can quickly give some answer.
Attachments:
model.vi ‏28 KB

Java Null Pointer Exception when assigning a value to an Object Array

I am working on a webservice where the request can contain a dynamic array of SingleOwnerRequestNodeDetail objects. I need to read these objects in and sort them according to an orderNbr that is contained in the object.
I am attempting to read these object into a Comparable class and sort them. I am having problems when I try to insert the objects into my object array ComparableBO[]. I get the following error: Exception during processing: java.lang.NullPointerException
Any assistance would be greatly appreciated.
Here's my class:
public class ComparatorBO implements Comparable {
     private SingleOwnerRequestNodeDetail nodeDetailInfo;
     private int orderNbr;
     public SingleOwnerRequestNodeDetail getNodeDetailInfo() {
          return nodeDetailInfo;
     public void setNodeDetailInfo(SingleOwnerRequestNodeDetail nodeDetailInfo) {
          this.nodeDetailInfo = nodeDetailInfo;
     public int getOrderNbr() {
          return Integer.parseInt(nodeDetailInfo.getSingleOwnerRequestOrderNbr());
     public void setOrderNbr (int orderNbr) {
          this.orderNbr = orderNbr;
     public int compareTo(Object anotherNodeDetailInfo)throws ClassCastException {
          if (!(anotherNodeDetailInfo instanceof ComparatorBO))
               throw new ClassCastException ("An single owner request node detail object is expected");
          int anotherNodeDetailOrderNbr = ((ComparatorBO)anotherNodeDetailInfo).getOrderNbr();
          return this.orderNbr - anotherNodeDetailOrderNbr;
}Here's the code where I read in the objects and attempt to place them in the comparableBO[]
ComparatorBO[] comparatorBOArray = null;
comparatorBOArray = new ComparatorBO[requestInfo.length];
          for (int i=0; i < requestInfo.length; i++)
               SingleOwnerRequestNodeDetail nodes = new SingleOwnerRequestNodeDetail();
               ComparatorBO comparatorBO = new ComparatorBO();
               nodes.setSingleOwnerRequestNodeID(requestInfo.getSingleOwnerRequestNodeID());
               nodes.setSingleOwnerRequestNodeType(requestInfo[i].getSingleOwnerRequestNodeType());
               nodes.setSingleOwnerRequestOpCode(requestInfo[i].getSingleOwnerRequestOpCode());
               nodes.setSingleOwnerRequestOrderNbr(requestInfo[i].getSingleOwnerRequestOrderNbr());
               comparatorBO.setNodeDetailInfo(nodes);
               *comparatorBOArray[i].setNodeDetailInfo(comparatorBO.getNodeDetailInfo());*
               comparatorBOArray[i].setOrderNbr(Integer.parseInt(nodes.getSingleOwnerRequestOrderNbr()));

imadeveloper wrote:
I am working on a webservice where the request can contain a dynamic array of SingleOwnerRequestNodeDetail objects. I need to read these objects in and sort them according to an orderNbr that is contained in the object.
I am attempting to read these object into a Comparable class and sort them. I am having problems when I try to insert the objects into my object array ComparableBO[]. I get the following error: Exception during processing: java.lang.NullPointerException
Any assistance would be greatly appreciated.
Here's my class:
public class ComparatorBO implements Comparable {
     private SingleOwnerRequestNodeDetail nodeDetailInfo;
     private int orderNbr;
     public SingleOwnerRequestNodeDetail getNodeDetailInfo() {
          return nodeDetailInfo;
     public void setNodeDetailInfo(SingleOwnerRequestNodeDetail nodeDetailInfo) {
          this.nodeDetailInfo = nodeDetailInfo;
     public int getOrderNbr() {
          return Integer.parseInt(nodeDetailInfo.getSingleOwnerRequestOrderNbr());
     public void setOrderNbr (int orderNbr) {
          this.orderNbr = orderNbr;
     public int compareTo(Object anotherNodeDetailInfo)throws ClassCastException {
          if (!(anotherNodeDetailInfo instanceof ComparatorBO))
               throw new ClassCastException ("An single owner request node detail object is expected");
          int anotherNodeDetailOrderNbr = ((ComparatorBO)anotherNodeDetailInfo).getOrderNbr();
          return this.orderNbr - anotherNodeDetailOrderNbr;
}Here's the code where I read in the objects and attempt to place them in the comparableBO[]
ComparatorBO[] comparatorBOArray = null;
comparatorBOArray = new ComparatorBO[requestInfo.length];
          for (int i=0; i < requestInfo.length; i++)
               SingleOwnerRequestNodeDetail nodes = new SingleOwnerRequestNodeDetail();
               ComparatorBO comparatorBO = new ComparatorBO();
               nodes.setSingleOwnerRequestNodeID(requestInfo.getSingleOwnerRequestNodeID());
               nodes.setSingleOwnerRequestNodeType(requestInfo[i].getSingleOwnerRequestNodeType());
               nodes.setSingleOwnerRequestOpCode(requestInfo[i].getSingleOwnerRequestOpCode());
               nodes.setSingleOwnerRequestOrderNbr(requestInfo[i].getSingleOwnerRequestOrderNbr());
               comparatorBO.setNodeDetailInfo(nodes);
               *comparatorBOArray[i].setNodeDetailInfo(comparatorBO.getNodeDetailInfo());*
               comparatorBOArray[i].setOrderNbr(Integer.parseInt(nodes.getSingleOwnerRequestOrderNbr()));
Well normally when someone wont tell me what line the error occured in I copy paste their code into my compiler and find out. But you have other classes which you have not shown us so I cannot help you.
Incase you missed my point, please tell us where the error occured!

Plotting an array with a large number of data points

Hello All,
I am collecting data every second for 24 Hrs. How do I plot this on a XY plot? I have the data collection setup in a while loop and my initial attempt was to use a shift register and a build array to make the array and that works OK. The problem is I do not know if this is a wise option in terms of memory usage. (I end up making 3 arrays and 3*86400=259200 data points in 3 shift registers).
What is the better way to plot 86400 data points in a XY plot? I am also writing the data to a file every second.
Thanks,
KB

Allan,
Thanks for the message. I am attaching with this message a ccpy of my vi where you can see that I am collecting data from 3 counters, writing them to a file and displaying them. Can you comment on this Vi with regard to memory management?
Yes, I would like to see your examples. Thanks once again.
KB
Attachments:
PC21.vi ‏418 KB

Problem with Point-Array

I made the following method:
Point[] makeLine (int length)
          Point[] newLine = new Point[length];
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to make a Line that randomly jumps and stuff.
Compiles fine, but when i want to run it i get a NullPointerExeption at
newLine.x = i;
when i comment that one out i get the same error on the line after .
I absolutely cant find the mistake, can anybody help me please?
Thanks in advance

You have defined an array, but you need to put objects into the array. i.e. when an array is created, every value is initlaised to null. The OO way to do this is
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Call library function node with array of clusters using array data pointer

Hello all.
I am writing a LabVIEW wrapper for an existing DLL function.
The function has, as one of its parameters, an array of structs. The struct is very simple, containing two integers. I am using the call library function node to access it.
In Labview I created an array of clusters, where the cluster has two 32-bit integers as its members. So far, so good.
Now I have to pass this in to the Call Library Function Node. Here I am running into trouble.
I have used The topic in LAVA and The topic in the knowledge base as my primary sources of information, though I have read a bunch of forum topics on the subject too.
I do understand that I could write a new function which takes as a parameter a struct with the size as the first member and an array as the second, and I might just do this and have it call the regular function, but I was hoping to do it more simply.
According to the C file which LabVIEW generates for me from the CLFN when I choose "Adapt to Type" and "Array Data Pointer", the prototype it is expecting is:
int32_t myFunc(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, void data[], int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex);
And the prototype of the function in my DLL is
int borland_dll myFunc(DWORD handle, usint channel,
int FIFOnumber, struct mStruct *data, int numWords, int *actualLoaded, int *actualStartIndex);
This looks like a match to me, but it doesn't work (I get garbage in data). From the topic in LAVA referenced above, I understood that it would work. It does not.
If I cast data to the pointer-to-pointer I get when I generate c code by wiring my struct to a CIN and generating, then I seem to get what I expect. But this seems to work when I choose "pointers to handles" too, and I would expect array data pointer to give a different result.
Is there any way to get this to work directly, or will I have to create a wrapper? (I am currently using LabVIEW 2011, but we have customers using 2009 and 2012, if not other versions as well).
Thank you.
Batya
Solved!
Go to Solution.

OK, here is more detailed information.
I have attached the VI.
This is the code from the "C" file created by right-clicking the CLN and creating a "C" file.
When the parameter in the CLN is set to "array data pointer":
/* Call Library source file */
#include "extcode.h"
int32_t Load_Transmit_FIFO_RTx(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, void data[], int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex);
int32_t Load_Transmit_FIFO_RTx(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, void data[], int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex)
/* Insert code here */
When the parameter is "pointers to handles":
/* Call Library source file */
#include "extcode.h"
/* lv_prolog.h and lv_epilog.h set up the correct alignment for LabVIEW data. */
#include "lv_prolog.h"
/* Typedefs */
typedef struct {
int32_t control;
int32_t data;
} TD2;
typedef struct {
int32_t dimSize;
TD2 data[1];
} TD1;
typedef TD1 **TD1Hdl;
#include "lv_epilog.h"
int32_t Load_Transmit_FIFO_RTx(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, TD1Hdl *data, int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex);
int32_t Load_Transmit_FIFO_RTx(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, TD1Hdl *data, int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex)
/* Insert code here */
When the parameter is set to "handles by value":
/* Call Library source file */
#include "extcode.h"
/* lv_prolog.h and lv_epilog.h set up the correct alignment for LabVIEW data. */
#include "lv_prolog.h"
/* Typedefs */
typedef struct {
int32_t control;
int32_t data;
} TD2;
typedef struct {
int32_t dimSize;
TD2 data[1];
} TD1;
typedef TD1 **TD1Hdl;
#include "lv_epilog.h"
int32_t Load_Transmit_FIFO_RTx(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, TD1Hdl *data, int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex);
int32_t Load_Transmit_FIFO_RTx(uint32_t handle, uint16_t channel,
int32_t FIFOnumber, TD1Hdl *data, int32_t numWords, int32_t *actualLoaded,
int32_t *actualStartIndex)
/* Insert code here */
As to the DLL function, it is a bit more complicated than I explained above, in the current case. My VI calls the function by this name in one DLL, and that DLL loads a DLL and calls a function (with the same name) in the second DLL, which does the work. (Thanks Rolfk, for helping me with that one some time back!)
Here is the code in the first ("dispatcher") DLL:
int borland_dll Load_Transmit_FIFO_RTx(DWORD handle, usint channel, int FIFOnumber, struct FIFO_DATA_CONTROL *data, int numWords, int *actualLoaded, int *actualStartIndex)
t_DispatchTable *pDispatchTable = (t_DispatchTable *) handle;
int retStat = 0;
retStat = mCheckDispatchTable(pDispatchTable);
if (retStat < 0)
return retStat;
if (pDispatchTable->pLoad_Transmit_FIFO_RTx == NULL)
return edispatchercantfindfunction;
return pDispatchTable->pLoad_Transmit_FIFO_RTx(pDispatchTable->handlertx, channel, FIFOnumber, data, numWords, actualLoaded, actualStartIndex);
borland_dll is just "__declspec(dllexport)"
The current code in the DLL that does the work is:
// TEMP
typedef struct {
int control;
int data;
} TD2;
typedef struct {
int dimSize;
TD2 data[1];
} TD1;
typedef TD1 **TD1Hdl;
// END TEMP
int borland_dll Load_Transmit_FIFO_RTx(int handlertx, usint channel, int FIFOnumber, struct FIFO_DATA_CONTROL *data, int numWords, int *actualLoaded, int *actualStartIndex){
struct TRANSMIT_FIFO *ptxFIFO; //pointer to transmit FIFO structure
usint *pFIFOlist; //pointer to array of FIFO pointers to FIFO structures
int FIFOentry, numLoaded;
usint *lclData;
usint nextEntryToTransmit;
// TEMP
FILE *pFile;
int i;
TD1** ppTD = (TD1**) data;
TD1 *pTD = *ppTD;
pFile = fopen("LoadFIFOLog.txt", "w");
fprintf(pFile, "Starting Load FIFO with %d data words, data pointer 0x%x, with the following data&colon; \n", numWords, data);
for (i = 0; i < numWords; i++) {
fprintf(pFile, "%d: control--0x%x, data--0x%x \n", i, data[i].control, data[i].data);
fflush(pFile);
fprintf(pFile, "OK, using CIN generated structures: dimSize %d, with the following data&colon; \n", pTD->dimSize);
for (i = 0; i < numWords; i++) {
fprintf(pFile, "%d: control--0x%x, data--0x%x \n", i, pTD->data[i].control, pTD->data[i].data);
fflush(pFile);
// END TEMP
if ((handlertx) <0 || (handlertx >= NUMCARDS)) return ebadhandle;
if (cardrtx[handlertx].allocated != 1) return ebadhandle;
pFIFOlist = (usint *) (cardrtx[handlertx].segaddr + cardrtx[handlertx].glob->dpchn[channel].tr_stk_ptr);
pFIFOlist += FIFOnumber;
ptxFIFO = (struct TRANSMIT_FIFO *)(cardrtx[handlertx].segaddr + *pFIFOlist);
//use local copy of ptxFIFO->nextEntryToTransmit to simplify algorithm
nextEntryToTransmit = ptxFIFO->nextEntryToTransmit;
//on entering this routine nextEntryToLoad is set to the entry following the last entry loaded
//this is what we need to load now unless it's at the end of the FIFO in which case we need to wrap around
if ( ptxFIFO->nextEntryToLoad >= ptxFIFO->numEntries)
*actualStartIndex = 0;
else
*actualStartIndex = ptxFIFO->nextEntryToLoad;
//if nextEntryToLoad points to the last entry in the FIFO and nextEntryToTransmit points to the first, the FIFO is full
//also if nextEntryToLoad == nextEntryToTransmit the FIFO is full and we exit without loading anything
if (( (( ptxFIFO->nextEntryToLoad >= ptxFIFO->numEntries) && (nextEntryToTransmit == 0)) ||
( ptxFIFO->nextEntryToLoad == nextEntryToTransmit)) && (ptxFIFO->nextEntryToLoad != INITIAL_ENTRY)){
*actualLoaded = 0; //FIFO is full already, we can't add anything
return 0; //this is not a failure, we just have nothing to do, this is indicated in actualLoaded
numLoaded = 0;
lclData = (usint *)data; //must use 16 bit writes to the module
//conditions are dealt with inside the for loop rather than in the for statement itself
for (FIFOentry = *actualStartIndex; ; FIFOentry++) {
//if we reached the end of the FIFO
//if the module is about to transmit the first element of the FIFO, the FIFO is full and we're done
//OR if the module is about to transmit the element we're about to fill in, we're done - the
//exception is if this is the first element we're filling in which means the FIFO is empty
if ((( FIFOentry >= ptxFIFO->numEntries) && (nextEntryToTransmit == 0)) ||
((FIFOentry == nextEntryToTransmit) && (FIFOentry != *actualStartIndex) )){
*actualLoaded = numLoaded;
//set nextEntryToLoad to the end of the FIFO, we'll set it to the beginning next time
//this allows us to distinguish between full and empty: nextEntryToLoad == nextEntryToTransmit means empty
ptxFIFO->nextEntryToLoad = FIFOentry;
return 0;
//we reached the end but can continue loading from the top of the FIFO
if ( FIFOentry >= ptxFIFO->numEntries)
FIFOentry = 0;
//load the control word
ptxFIFO->FifoData[FIFOentry * 3] = *lclData++;
//skip the high of the control word, the module only has a 16 bit field for control
lclData++;
//now put in the data
ptxFIFO->FifoData[(FIFOentry * 3) + 2] = *lclData++;
ptxFIFO->FifoData[(FIFOentry * 3) + 1] = *lclData++;
numLoaded++;
//we're done because we loaded everything the user asked for
if (numLoaded >= numWords) {
*actualLoaded = numLoaded;
ptxFIFO->nextEntryToLoad = FIFOentry+1;
return 0;
//if we reached here, we're done because the FIFO is full
*actualLoaded = numLoaded;
ptxFIFO->nextEntryToLoad = FIFOentry;
fclose (pFile);
return 0;
As you can see, I added a temporary diagnostic with the structures that were created in the "Handles by value" case, and print out the data. I see what is expected, whichever of the options I pick in the CLN!
I understood (from the information in the two links I mentioned in my original post, and from the name of the option itself) that "array data pointer" should pass the array of data itself, without the dimSize field. But that does not seem to be what is happening.
Batya
Attachments:
ExcM4k Load Transmit FIFO.vi ‏15 KB

Pointer to array

Hello,
I'm having some trouble in sending a pointer to a predefined array through
the GPIB using labview (6i).
Is there any way to create an array and a pointer to it in labview
without going through the call library functions? Even if that were the
only way, can anybody help me to get started?
Thank you very much for your help,
Riccardo

Are you trying to send some data to an instrument?

I have two arrays of points, when i plot them there´s an intersection point, but this point doesn´t belong to any arrays...

I have two arrays of points, when i plot them there´s an intersection point, but this point doesn´t belong to any arrays. I need to find the both value of this point, X and Y. I attached my problem in a very simple example. Thanks.
Attachments:
arrays_plot.vi ‏25 KB

Although this doesn't directly answer your question , I've attached a VI that will hopefully give you a start and point you in the right direction. It generates a Boolean array that indicates between which indecies an intersection has taken place. Then, all you need to do is use triganometry to work out exactly what the intersection point is.
Copyright © 2004-2015 Christopher G. Relf. Some Rights Reserved. This posting is licensed under a Creative Commons Attribution 2.5 License.
Attachments:
2x1D_Array_Intersections.vi ‏36 KB

How to make an acquired array of data work with point-by-point functions

Hello everyone,
I am working on a LabVIEW project using the Measurement Computing PCI-DAS6402/16 board. I am attempting to use point-by-point analysis with data acquired from the board, but I am having some difficulty. I am currently only able to acquire an array of data and not just a single point of data per scan. So, I was wondering if i) anybody possibly had any knowledge/experience using this particular board and getting it to be compatable with point-by-point VIs or ii) if anybody possibly knows anyway to convert an array of acquired data to work with point-by-point VIs in a hard realtime application. Thanks
Pat
Message Edited by Support on 11-16-2005 07:56 AM

Hi Pat
I just can tell you how you can use the pt-by-pt functions. As you said you have an array of data. To use the pt-by-pt functions, you need the single datapoints. So the only way is to use a loop to get the single elements and pass them to the pt-by-pt functions.
I've attache a simple example.
If this is the right way for you concerning processor and memory load, execution speed etc. I can't tell you.
Hope this helps.
Thomas
Using LV8.0
Don't be afraid to rate a good answer...
Attachments:
PtByPt.vi ‏17 KB

How to get the memory address of an array (pointer in C)?

I am writing an application that exchanges data with a PXI device via DMA. Basically I will provide it a memory address and a direction, and it transfers the data. I would like to give it the memory location of an array in LabVIEW, but I do not know how to get the memory location without doing a DLL call to C code that returns the pointer. Is there an easy way to do this in LabVIEW? Any help is much appreciated.

A similar question was asked recently regarding strings. You cannot pass pointers in LabVIEW as you do in C. You can pass an array to a DLL, but that means you would need to write a wrapper DLL. Be sure to read the section in the LabVIEW Help on calling code from text-based languages and also take a look at the "Call DLL" example that ships with LabVIEW - it contains many examples of how to deal with various datatypes.

Getting element of array returns a pointer?

Hi to All,
I have a code:
/tt [[0 1 2] [10 11 12] [20 21 22]] def
tt 0 get    /ttr exch def          % ttr = [0 1 2]
ttr 2 777 put                      % ttr = [0 1 777]
tt pstack                          % tt = [[0 1 777] [10 11 12] [20 21 22]]
I thought tt should not be changed. But it is. Why is this? How may I avoid this?
Thank you in advance,
JackK

In addition, try this. Composite objects (arrays, dictionaries, strings) are allocated from a potentially limited pool of memory so the programmer has full control of the memory allocation process. Only specific operators such as array, string, dict will allocate memory (and the parser as it sees literals of these types). So, if another operator returns a composite object, it follows that no memory was allocated, and it was not copied. It is therefore a reference to the original (a pointer, if you prefer, though PostScript avoids the term).
If you're a C programmer it can help to think of PostScript objects as 8 byte structures. A structure could (but would not exactly) contain the object type and simple value. For an array, the structure would contain the type and a pointer to the array memory, length and offset. The array memory is a list of 8 byte structures.
getinterval makes a new object (8 byte) containing a pointer to the same array memory, but a different length and offset.
get returns a copy of one of the 8 byte structures from the array memory. For a simple type (e.g. real) this copy is complete and separate. If the element is an array the 8 bytes are copied, but the pointer to the array memory, length and offset are unaltered. Essentially it is the same array.
Indeed, if you translated this example to C it would be the same array.

Null pointer with array

Please help! I'm new to Java and have done the following:
Created an array to hold 100 records.
Created 5 records for the array (index 0, 1, 2, 3, 4)
Now I'm trying to use a for loop to have a write output of the array values and I'm getting a NULL pointer exception.
Any ideas???

When an array is initialized, all its values initially point to null (except for primitives, which point to their respective 0's).Try printing out the index of the value before you print the value - it should fail at index 5. If you want to end the for-loop at the first null entry, use
for(int index = 0 ; index < array.length && array[index] != null ; index++)
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}if you only want to print out non-null values, and skip all the rest, instead use
for(int index = 0 ; index < array.length; index++)
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      array[index].doStuff();
}

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