Issue 73490

Created attachment 42177 [details]
screenshot of spreadsheet with diagram

As an example, I would like to be able to access the function value at position
3,4 in the attached diagram (attachment 42117 [details]).

->schlotter: Do you want to get information about the coordinates of an interpolated point while moving 
over it with the mouse? Or what do you mean by "pull out" in the summary?

->bm: I would like to access the curve's points from the spreadsheet.  The best
thing would be to be able to access the curve like a function/macro from the
spreadsheet.  So that I can enter e.g. DIAGRAM1(3.4) in the spreadsheet which
will evaluate to the y-value of the curve at x-value 3.4.

@BM: What do you think about this feature issue?

->schlotter: You can access the values of a regression curve (trend-line) by
calculating the regression formula in Calc. Accessing the points calculated
inside a diagram has some difficulties:

1. You have to address the chart. This could be "by name", if you gave the chart
a name

2. You have to address the fuction. So you would need to say which data series
you want calculated values from. And what part: the series itself, a trendline,
the error bar's value etc.

3. Passing of values in this direction does not yet exist. Charts are usually
not loaded immediately, what you see is a replacement image. Even if the chart
is loaded, the calculation is done by the view component, which you usually only
have once you activated the chart.

4. The suggested feature only makes sense for scatter/line charts with splines.
I think that is not worth the effort. (For lines calculation is so easy, that
you can do it with a simple formula).

5. The chart's purpose is the visualization of data, Calc is used for
calculating values. I would like to stick with that.

If there is not a connection between Chart and Calc, let me precisely state what
my exact problem is (I will just copy it over here from the forums[1]):

<begin quote>
1.) I generate a sheet with the following data

1 1.4
3 5.7
6 2.6

2.) Then I select the data and go to Insert -> Chart

3.) As chart-type I choose XY-Chart

4.) As variant I choose cubic spline with symbols

5.) After that a chart pops up

6.) I right-click on that chart and choose Chart Type...

7.) There I have the possibility to change the resolution of the fitting graph
(the spline)

8.) Let us choose 3 for the resolution (just as an example)

9.) After clicking OK I can clearly see the effects of the lower resolution and
I can see the points
that OpenOffice has calculated to draw the fitting graph (the spline)

10.) MY PROBLEM NOW IS: What coordinates do these points (that OpenOffice has
calculated to draw the spline) have?
<end quote>
(I use the German version of OOo 2.1, so probably not all option and menu names
above are correct.)

[1] http://www.oooforum.org/forum/viewtopic.phtml?p=202517#202495 

So you want to see the calculated values of a curve created by a chart. (Changed
subject to reflect that better).

I think a feature that allows you to display the (x/y) pair for points on the
curve in the status bar according to the mouse cursor position, seems realistic.
To query those points via an API from a chart seems quite an effort for a
feature that doesn't look to me like a largely wanted one. Let's see if anyone
votes on this issue.

Just seeing the (x/y) pair in the status bar would not be enough.

My example above was a simplified case.  In reality, of course, I would increase
the resolution to have many more data points.  In this case, it is not possible
to transcribe hundreds of data points by hand.

Maybe this feature can be accomplished without establishing a link between Calc
and Chart?  I think of a functionality in Calc that can interpolate a set of
numbers according to a given "rule".  This feature would allow me to select the
interpolation rule "cubic spline" which would then let me specify the
resolution.  After confirmation, the feature would fill a column with
interpolated data points.  This would create data points the same way Chart
does, but would otherwise be totally independent.

The downside of this approach is that it (probably) leads to duplicate code
which basically does the same thing.

change owner