signal processing and fft

I collected signal data from labchart and plotted it in matalb,but my end goal is to get an fft of that signal or graph that I plotted.I was wondering how can I accurately get and fft of that plot.

[Walter Roberson]

Do you still have the data that was being plotted, or could you modify your program to save it?

If not then do you still have the graphics objects that went into making up the parts of the plot?

If not then is all you have a screen capture of a line plot?

[Mugisha Nitunga]

I have the raw data that I extracted from the labchart signal and the signal which is in labchart.

Answer 1

[Star Strider]

See the documentation for the fft (link) function. Particularly note the code between the first (top) two plot figures.

[Mugisha Nitunga]

thank you, so is it possible to just get the specific signal section from labchart and directly plot it in matlab then get the fft?

[Walter Roberson]

Just take the data you collected and fft it (or otherwise process it as appropriate, such as spectrogram())

[Star Strider]

My pleasure.

Since you plotted the original data in MATLAB, you have the data. If you know the independent variable range that you want to analyze, you can use the find function to determine the indices for the variable range, and then just use those indices to access your independent and dependent variables.

If you want to do it graphically, in the plot figure window, you can use the ‘Data Brushing’ tool to select specific data from the plot, then save them to the Clipboard to analyze separately. See the documentation on Marking Up Graphs with Data Brushing (link) for details.

Once you get the data you are interested in analyzing, you can do the fft on it.