Extract data from chart

[MC盗版用户]

Hi,

Usually, data are given by a chart/figure in picture form, such as JPG,TIF,BMP,PNG...

Like below, it is the V-I charactristic of a diode.

I want to get the V and corresponding I value, then I can get a fit function V(I) (or I(V) ).

Although,we can read several more exact points by eye-measurement, and then get a fit function. I think the fit function will be more precise if we read more points.

How can I do to extract as much points as possible? Any help will be appriciated.

My MC version is "Mathcad 15 F000".

[RichardJ · Accepted solution]

This should help.

[MC盗版用户]

So funny. Let me see.

Thank you!

[MC盗版用户]

Why don't clean the curve to get rid of useless points fistly by some tools,like mspaint or photoshop?

[Werner_E]

盗版 用户 wrote:

Why don't clean the curve to get rid of useless points fistly by some tools,like mspaint or photoshop?

Feel free to do so. The sheet Richard sent is an attempt to be a standalone approach. If you are willing to use third party software, you may chose to use a program like DataThief right away.

Alvaro Diazo one posted a sheet long time ago which enabled you to do some kind of manual digitizing. Maybe of interest. The most recent link I could find is this where Norm reposted it: http://communities.ptc.com/message/226096#226096

[MC盗版用户]

Thank you.

Deal with the scale of the XY axes is another queary. In my figure Y axis is logarithmic scale, but yours are linear.

Let me seeeeee

[RichardJ]

I personally don't use the sheet at all. I posted it because you asked for a solution in Mathcad. I have a piece of software called Un-Scan-It, which does a much better job. And yes, I sometimes clean the image up in Photoshop or Photopaint first.