calculate a derivative on a graph

what code would i need to answer my question?

[Walter Roberson]

What is our input? Is it an image of a plot ? Is it graphic objects that could be examined to extract their data? Is it the data itself?

Is there a model of the form of the equation, or is it necessary to somehow deduce the equation from the graph ?

[Thomas]

its a graph, need to find the derivative at intervals of the graph

[Sulaymon Eshkabilov]

Is it MATLAB figure object or an image?

Answer 1

[Walter Roberson]

There are two steps:

1. First you have to extract x and y data from the graph. If the graph is in the form of an image, then extracting the data by having code analyze the image can be a bit tricky, but there are a number of File Exchange contributions to try to make it easier. If the graph is in the form of MATLAB graphic objects, then you can extract data from those by examining their XData and YData properties. And if you have the x and y data available in the workspace, use that directly.
2. Once you have the x and y coordinates, use gradient . Possibly followed with interp1