read data from graph

[sjh]

Is it possibe to read data directly from a graph? is there a function where you can specify the X scale value and it will read the 'y' from the graph?

[BryanL]

Hi SJH, please give more background of your application.  Do you mean you have a third party graph, and you need get read out X Y values, or you have the graph composed yourself?  If it is the later case, you should already have your X and Y data array, you may need to do a fit to the XY valuses and then using the resulting function to calculate Y from X assuming you are not just after the data points in your array.  If a fit is not possible, you would need to some interporlation between points of interests.

[sjh]

It is a 'labview' xy graph created using 3 sets of xy coordinates.   I need to be able to read off intermediate points between those plotted. 

There are a number of ways to do it - linear fit between points, interpolation ...but labview does it already and it is possible to read off via the cursor.

It would be nice to be able to link into the cursor function as part of the programme.

[BryanL]

If cursor is good enough for your data read, the attached VI may help.

[sjh]

I am running in 6.0 - could you post a diagram?

Thanks

[BryanL]

Too bad I dont have LV2009 installed on this sytem, maybe someone using 2009 can help by getting a vi snippet of the diagram.

[BryanL]

I put the diagram onto a PDF file

[sjh]

Thanks very much. - That is a useful bit of code. But I am not sure that it will do what I need.

I would like to enter 'automatically' a series of 'X' co ordinates and then read off the corresponding Y from the plot.

SJH

[BryanL]

If linear interpolation is acceptable, you can do that with the XY array you have. I would not think in terms of reading data from graph, but the data array instead.