Simple Line Chart - Values over time

Question

A simple line chart displaying a set of values over time would seem to be a very easy report to design. I'll be darned if I can see how to design it. Can anyone shed some light?
I have provided links to a report and a spreadsheet which is the report datasource. My actual report will use SQL Server as its datasource. I am providing ths excel based example for the sake of protability.You will need to set the datasource location after saving the files to your hard drive.
I can get the lines to draw properly, what I cannot figure out is how to specify the datetime values for the x axis. The column I would like to use on the x-axis is called DerivedLoggingTime.
I'd also like to get control of the logarithmic algorithm used to formulate the y-axis values. I am not always happy with the values that the log algorithm comes up with.
Any help is greatly appreciated.
[Link to report|http://www.usol.com/~joe/linechart.rpt]
[Link to spreadsheet|http://www.usol.com/~joe/AnalysisResults.xls]
Another discovery while working on this report - our database will be SQL 2008 and  we are making use of the datetime2 datatype. CR appears to be treating this datatype as text. So when working with the SQL based datasource, I had to cast datetime2 columns as datetime in order for CR to see the columns as datetime instead of text. This is fine in this instance because the granularity of the datetime values for this particular report does not require datetime2, but that will not always be the case. CR will need to recognize the new datatype.
Edited by: Joe Sytniak on Jul 17, 2008 5:37 PM

Answer 1

Hi Joe,
The Date Axis Line Chart of the Numeric Axis Type Chart, can be used to display data on a regular interval of days, Months and Years. The information displayed can unfortunately not be more granular that days.
This type of chart is generally used when the data is recorded on irregular intervals in the database, and to make sense of the information stored it needs to be displayed at regular intervals.
Since the data stored in your data source seems to be stored every 4 minutes, it will not be necessary to use this type of chart. I will suggest to use the regular line chart instead.
To create a line chart using your date time field and value:
1. Select "Chart" under the menu "Insert"
2. Insert the chart on your report in the desired section.
    ( Group Header # 3 in your case. )
3. In the "Chart Expert" window, under the tab "Type",
    change the chart type to a line chart by selecting "Line" in
    the "Chart Type" list.
4. Under the tab "Data", add the database field that contains the Date Time information under the "On change of" list.
(In your case, add the "DerivedLoggingTime" database field)
5. To display the data for each minute, select the database fields you just added under the "On Change of" list, and
click on the button "Order". In the "Chart Sort Order" window,
select "For each minutes" in the "Section will be printed" drop down list, then click "OK"
6. Add the field you want to display the value in the "Show Value List", then click "OK"
Now it will display a line chart as desired, but since there is a lots of data point on your chart, the x axis date time labels will overlap each other. To avoid  this situation, I will suggest to skip labels.
To format a chart to skip labels:
1. In the "Preview" tab of the report, select one of the x axis label, and right click on it. In the contextual menu, select "Group (X) Axis Options..."
2. In the "Group (X) Axis Settings" window, under the tab "Layout", check the option "Skip Group Labels" and set the value to 15 for example.
Now, it will display the date time label at every 15 data point.
As for your question on how get control of the logarithmic algorithm used to formulate the y-axis values, we unfortunately do not have much control over it other than:
- Entering static values, or
- Checking or Unchecking the option "Use Logarithmic scales"
The above options are available on the y axis. To change those options:
1. In the "Preview" tab of the report, select one of the y axis label, and right click on it. In the contextual menu, select "Group (Y) Axis Options..."
2. In the "Group (Y) Axis Settings" window, under the tab "Scales", you will see the following options:
- Minimum Values
- Maximum Values
- Use Logarithmic scales
I will suggest to check the option "Use Logarithmic scales"
Finally, as for the issue you discovered where SQL Server 2008 data type DateTime2 is converted to a string in Crystal Reports 2008, it is important to note that SQL Server 2008 hasn't been released yet, therefore it has not been tested in Crystal Reports 2008. Once SQL Server 2008 is released, I will suggest to test it again using the ODBC driver provided with this new version. 
At this point I am assuming that this is happening because it is a new data type and an unknown data type get converted to string.