Re: Subtract consecutive values in an array

Posted by jerie on Oct 20, 2016; 12:06pm
URL: http://imagej.273.s1.nabble.com/Subtract-consecutive-values-in-an-array-tp5017426p5017431.html

Hi Volko,

how about converting the array into an image, duplicate it, add one pixel
to each copy at beginning/end and subtract the images?

Abraços, Jens

Dr. Jens Rietdorf, visiting scientist @ center for technological
development in health CDTS, Oswaldo Cruz Foundation Fiocruz, Rio de Janeiro
Brasil.

On Thu, Oct 20, 2016 at 5:12 AM, Volko Straub <[hidden email]> wrote:

> Dear All,
>
> Is there a simple method in a macro to subtract the first value in an
> array from the second value, etc? This could obviously done by writing a
> for-loop and iterating through the array, but that seems to be a bit
> clumsy. Is there a more elegant way that I am missing?
>
> Here is what I try to achieve:
> Let's assume, I have the following array [6,9,4,3,5,...]. I would like to
> calculate an array that contains the difference between consecutive
> elements in the original array, i.e. [3,-5,-1,2, ...] or more generally
> [x1-x0, x2-x1, x3-x2, ...]. Obviously the new array would need to be one
> element shorter than the original array as there is nothing to subtract
> from x0.
>
> Perhaps this could be achieved by shifting all elements in an array by one
> index position and then subtract the original array from the shifted array,
> but I don't seem to work out whether this is possible within a macro.
>
> Any suggestions/pointers would be very welcome.
> Thanks,
> Volko
>
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