Given only an image of a chart, estimate the data associated with it

This add-in is designed for those instances when one has an image of a chart but not the underlying data.  Once the image is in electronic form, this add-in can help estimate the values of the associated data.

The compressed files

If you need help downloading and installing the add-in, read on.

1. Download the tm_chart_image_to_data.zip zipped file by clicking the link above.
2. Use WinZip (or a competing product) to extract the TM Chart Image to Data.xla file.
3. Run Excel and select Tools | Add-Ins...  Click the Browse... button.  Locate the file extracted in the previous step.  Ensure that the 'TM Chart Image to Data' entry in the Add-Ins list has a checkbox next to it.
4. The add-in will add a new menu item TM to the Worksheets menu bar.
5. Under TM, you will find a Chart Utilities | Data from Chart Image... entry.  Select it to bring up the dialog box.

Using the add-in

Upon selecting TM | Chart Utilities > Data from Chart Image... the default dialog box will show up.

This add-in only works with a chart that has linear axis.  That rules out its use with any variant of a log chart or other charts with a non-linear axis.  Note that a linear axis is not the same as a linear series.  The plotted series can be any kind.  It is just the axes that have to be linear.

Click the Get New Image button to load a new image of a chart.  This will also trigger a calibration process.  This will help the add-in track how the various points on the image map on to the actual values of interest.  This four step process separately identifies each of the X-minimum, X-maximum, Y-minimum, and Y-maximum values.

The image below shows the first point to be calibrated.  In the first of four steps, enter the minimum x value (zero in this case) and after the Input dialog box closes click on the x-axis location that corresponds to this value.  The next 3 steps in the calibration process identify the other three critical locations.