File Exchange > Graphing >    Tangent

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Draw a tangent line at selected point of a data plot.

Screen Shot and Video:

This app draws a tangent line at selected point of a data plot in a graph. A smoothing option is available for computing the derivative for noisy data.

Download the file Tangent.opx, and drag and drop it onto the Origin workspace. An icon will appear in the Apps Gallery window.


  1. Click the icon to open dialog. Change dialog settings as desired and press OK. A vertical line will be added to the graph.
  2. Drag the vertical line to select a desired point on the curve. The tangent line will update as you move the vertical line.
  3. Press the triangle button at the top right of the graph to display a context menu. Select "New Output" to add tangent line at currently selected point.
    You can then move the cursor to other points on the curve to add additional tangent lines.
  4. Select "Preferences..." from the context menu to re-open the dialog to change settings.
    When dialog is open, press "?" button, or F1 to open the help file.


It is best to use this app in Origin 2019B, or higher version. For lower version than Origin 2019B, if the plot is xy-exchanged, the horizontal for selecting data point is not able to be moved vertically by draging the line itself. The way to make this line moved is to drag one of the two handles, and even dragging the handle, the line would not move with the handle together, but it would jump to the position of the handle after the dragging done.


11/17/2015 v1.1 Supports duplicate values in x data.
8/16/2018 v1.2 Fixed bug for wrong data with multiple plots, support for Chinese version.
3/19/2019 v1.3 Support apparent tangent and xy exchanged graph
20/6/2019 v1.4 Change minimum version to Origin 2016
22/6/2020 v1.5 Fixed localization issue for Japanese

Reviews and Comments:




09/27/2020OriginLabHi wanghantechnion, you can drag the red vertical line to select another data point on the curve.

09/27/2020wanghantechnionWhen I click the "Tangent", a vertical line appears, but it shows "invalid tangent point", there is no desired point or chosen point appear. How should I do?

09/03/2020OriginLabHi 123-321,

Once you have gotten the slope value using this app, you can add the perpendicular line by selecting "File: New: Function Plot: 2D Function Plot" and enter the function body below in the Create 2D Function Plot dialog:

Select "Add to Active Graph" at the left-bottom corner and click OK button.

OriginLab Support

09/03/2020123-321Hi! Can anyone suggest how to draw a normal from a point on a curve (i.e., a perpendicular to a tangent)?

08/31/2020OriginLabHi ruhmblogger, you can drag and drop the *.opx file to the grey area once you launch Origin. Or you can select menu Tools: App Center and search this app to download and install it directly.

OriginLab Tech Support

08/30/2020ruhmbloggerI ve got no idea in which exact folder I should drag the .opx - there is no folder named: workspace in my applications. and I dont know forwhich symbol I need to look for.