Cut off some data from a set of data

Question

I have a set of data our of from power spectral density measurement.
I want to curve fitting with the data.
But I want to cut off below a certain frequency.  For instance, the PSD
data
contains {(1,10),(2,3),(3,4),(4,3),...} and I want to fit from 3 Hz
{(3,4),(4,3)...}.
I tried high pass filter but it does not change.  I tried several ways such
as
get time stamp and find the index for the element and remove the array
using
'Array'tools.  It cuts off the data sets that I wanted to remove but it
does
not remove the frequency values.  So it works like {(1,4),(2,3)....}
instead of
{(3,4),(2,3)..}.  Please let me know how I can make this work.
Thanks.
Attachments:
new-PSD-factor-v3.vi ‏522 KB

Answer 1

Hey Arrow,
I think I understand your question better now. You'll want to use the "delete from array.vi". It can be found by going to all functions>>Array. You'll need to input the array to be edited, which index to begin deleting from and how many elements to delete. From your application it sounds like you'll want to start from element zero and delete the number of elements that corresponds to 0 through 4 Hz.
In addition, you'll need to create an array that represents the frequencies you want to plot (4 1000 Hz or your upper limit). There'll need to be one frequency on your x axis for each element in your PSD array. Then bundle the two arrays together and plot them on an XY plot. You can use the "bundle" vi to accomplish this. You can find examples using clusters from help>>find examples. Then navigate to Fundamentals>>Arrays and Clusters.
Hope this helps out.
Chris Cilino
National Instruments
LabVIEW Product Marketing Manager
Certified LabVIEW Architect