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From: M.E.L. on 29 Apr 2010 16:20
I'm new to Matlab and still unsure as to how to create loops. I want to make a loop that will run through each value in the array and compare consecutive values. If the difference between consecutive values is greater than pi, I want to add 2*pi to the second value. If the difference between consecutive values is less than -pi I want to subtract 2*pi from the second value. How might I go about doing this?

Thank you!
From: dpb on 29 Apr 2010 16:32
M.E.L. wrote:
> I'm new to Matlab and still unsure as to how to create loops. I want to
> make a loop that will run through each value in the array and compare
> consecutive values. If the difference between consecutive values is
> greater than pi, I want to add 2*pi to the second value. If the
> difference between consecutive values is less than -pi I want to
> subtract 2*pi from the second value. How might I go about doing this?

You don't need loops most of the time in Matlab--that's the beauty of it...

x = some_values;
dx = diff(x); % sequential differences
idx1 = find(dx>pi);
x(idx1) = x(idx1+1)+2*pi;

idx2 = find(dx<-pi);
x(idx2) = x(idx2+1)-2*pi;

You may have to do this repetitively, however...

--


From: Roger Stafford on 29 Apr 2010 16:48
"M.E.L. " <schrodingers.lyon(a)gmail.com> wrote in message <hrcpm8$def$1(a)fred.mathworks.com>...
> I'm new to Matlab and still unsure as to how to create loops. I want to make a loop that will run through each value in the array and compare consecutive values. If the difference between consecutive values is greater than pi, I want to add 2*pi to the second value. If the difference between consecutive values is less than -pi I want to subtract 2*pi from the second value. How might I go about doing this?
>
> Thank you!

There is a matlab function called 'unwrap' which will do that whole job for you in one line.

xnew = unwrap(xold);

Roger Stafford
From: us on 29 Apr 2010 17:02
"M.E.L. " <schrodingers.lyon(a)gmail.com> wrote in message <hrcpm8$def$1(a)fred.mathworks.com>...
> I'm new to Matlab and still unsure as to how to create loops. I want to make a loop that will run through each value in the array and compare consecutive values. If the difference between consecutive values is greater than pi, I want to add 2*pi to the second value. If the difference between consecutive values is less than -pi I want to subtract 2*pi from the second value. How might I go about doing this?
>
> Thank you!

just want to make sure you'll also look at these

help for;
help while;
help end;

us
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