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Re: Finding a linear trend for mapped rainfall data

Hi Nathan,
First, you need to have the data in Ferret.  Do you have a single list
of data, which is rainfall versus time?  Once you have that, you can
run the regresst.jnl script.  Say your variable is called rain, then

  yes? let p = t[gt=rain]
  yes? let q = rain
  yes? plot rain        ! just plot the time series to see what you have
  yes? go regresst

      !  Now, the variables slope, intercep, qhat, and rsquare hold
      ! the results of the linear fit.

  yes? plot/sym q                ! this shows the original data as a scatter plot
  yes? let myline = p * slop + intercep
  yes? plot/vs/over p, qhat  ! the linear fit.

And so forth.

Nathan Toombs wrote:

How do I use ferret to find linear trends over time for all the regions of a map showing rainfall? The data file contains maps of rainfall over 100 years.


P.S. I’ve tried using the regression functions but can’t figure out how to use them.

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