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.

For more details on the installation process, see Common Installation Instructions for Office add-ins

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.

Once all four points are calibrated, click on the form to get the corresponding (X, Y) values.  The results will be in a new workbook.