Converting datacursor readings to log values.

I'm using an application which presents a curve with a logarithmic X-scale. The image is small and the scale divisions do not allow me to read the values accurately. I have enabled DataCursorMode, which is linear, and would like to convert these readings to be able to read the X points on the curve, but have been unable to determine the correct conversion factor. Advice will be appreciated. Thanks Stan

[per isakson]

I don't understand your question

Are you trying to define a function for

    'UpdateFcn', function handle
    Reference to a function that formats the text appearing in the
    data cursor.

or

    >> log10(10^3)
    ans =
         3

[dpb]

I don't follow, either -- if I do an example semilogx plot and turn on data cursor mode, I see x,y values in actual units, not y, log(x).

Or was the plot generated from log values as a linear plot, maybe? In that case it's 10^x_value (Per's second example).