This gadget is used to plot the tangent line along a select portion of a curve. It not only supports to specify the X data range of the curve, but also supports to select the Tangent point by the red vertical line. Even if the tangent line is not well-fitted to the curve, we can use smoothing methods to affect the calculated derivatives. And it is easy to output the result to a report.
1) Save the attached Tangent.opx, drag and drop it onto the Origin workspace (Need Origin 9.0 SR1) to install it.
2) Access this gadget by selecting Gadgets: Tangent from top menu.
After install the Tangent.opx, a CHM help file will be added to the \X-Functions\Data Exploration sub folder of your User Files Folder.
Please refer to the Tangent.chm help file and learn how to use.
In Origin 9.1, you could press F1 key to open the help file, when the Tangent setting dialog is open.
In Origin 9.0, the F1 key does not work. You need to find this Tangent.chm manually under \X-Functions\Data Exploration sub folder of your User Files Folder.
If you are using Origin 7.5 or 7.0, you can refer to the Tangents tool created by Michael Buess in File Exchange which plots the tangent to a curve at a selected point and reports the slope.