Problem on XY Regression Chart

[Former Member]

Hi All,

I created an XY Regression Chart which shows a straight line extrapolating the points plotted. Now for this line of type Y=mX + C, I want slope(m) and y-intercept(C) to be displayed on Applet. Does XY Regression Chart provide this facility.If so, could you please explain how to accomplish this?

Regards,

Ravi Kumar

[Former Member]

Hi All,

This is just an addition to above post. Does xMII used Method of Least Squares for Curve fitting the Regression straight line in XY graph. I had searched in xMII help file but did n't get any break through.

Any suggestions on above really appreciated.Thanks.

Regards,

Ravi kumar.

[Former Member]

Right Clicking on the chart and navigating to Data--->Statistics would give you some idea on the behaviour of the chart.

Other than that I am not sure how one can extract the calculated values and use them further.

For example the BL Services have actions defined for SPC Analysis which helps applications to further make use of the calculated values but I could not find anything similar for regression statistics.There definitely would exist (hidden)ways of accomplishing this.

As far as "Least Squares " is concerned , I would think because linear regression is based on this concept /rule, even MII would follow that.

Is there any other method, that you are aware of, that is used for linear regression?

[Former Member]

Yes, it uses the least squares approach (I wrote the code for it in xMII!) either with or without a zero-based intercept.

[Former Member]

Hi Rick,

Thanks for that info.

My query sometimes gives me null values but even then xy chart is getting developed which is OK as it is not showing the point on the plot.

But can you tell me how xMII does the slope and intercept calculation for plotting if in case query output has null values.

Does xMII provide any method for getting slope and intercept of XY Chart?

This is just to make sure that if in case we need to go for writing a procedure for slope and intercept calculation it is on par with xMII calculation.

Regards,

Ravi Kumar

[Former Member]

We have an XY Regression iChart configured, but the Data>Statistics right-click menu item is disabled. How dow we enable this Statistics menu item? Specifically we want to retrieve the Regression and the R-squared statistics.

[jcgood25]

The Data Statistics is really only relevant for a tag query. It will do a Tag Query Statistics query to an iChart image with MIN,MAX,TWA methods. This is the 'statistics' similar to 'current' that you can get from the iChart at runtime when viewing the typical Tag based line trend.

This is not the same as statistics will give you on an SPC Chart.

The XY Chart is what it is u2013 it either draws the regression line or not based upon the chart type, but the values or column of data is not accessible via script. The Linear Regression action inside BLS (misc. function category - http://help.sap.com/saphelp_xmii120/helpdata/en/45/a3cbb8c3b50cefe10000000a114a6b/frameset.htm) does give you access to the numbers for the line (adds a column called Predicted). It also gives you access to summary stat numbers for Intercept, Slope, R, and RSquared. This resultset could be charted as well because the output looks just like a tag query with a calculated column for the regression line.