Remap values of 256x256 array based on ranges

2 views (last 30 days)
done like this
if (n_rounded>=-90.0) && (n_rounded<-67.5)
n_rounded=-90;
elseif (n_rounded>=67.5) && (n_rounded<90.0)
n_rounded=-90;
elseif (n_rounded>=-67.5) && (n_rounded<-22.5)
n_rounded=-45;
elseif (n_rounded>=-22.5) && (n_rounded<22.5)
n_rounded=0;
elseif (n_rounded>=22.5) && (n_rounded<67.5)
n_rounded=45;
end
getting error Operands to the and && operators must be convertible to logical scalar values.
  1 Comment
Matt J
Matt J on 22 Feb 2016
Edited: Matt J on 22 Feb 2016
  1. You cannot apply && and to non-scalars. You could use & and |.
  2. if...else commands do not distribute through the elements of an array

Sign in to comment.

Accepted Answer

Stephen23
Stephen23 on 22 Feb 2016
Edited: Stephen23 on 22 Feb 2016
The basic problem is that both logical short-circuiting operators || and && operate on scalar value only. Here is an example:
>> false || true % both operands are scalar -> okay!
ans =
1
>> false || [true,false] % scalar and vector -> error!
Operands to the || and && operators must be convertible to logical scalar values.
So clearly your n_rounded is not a scalar, as the inputs to the || and && operators are non-scalar. You can remove this error this by using standard or | or and & operators. Then you will meet another behavior that confuses many beginners: all elements must be true for an if to run:
if [true,false]
disp('this will never run')
end
if [true,true]
disp('this code will run')
end
Alternative Solution
Simply vectorize whole thing and use histc:
>> n_rounded = 180*rand(5)-90
n_rounded =
-14.8919 -1.9345 50.4454 -66.2448 -47.7396
-81.0622 -29.2105 -19.8470 79.5691 -26.4315
72.4889 72.0097 -46.4956 82.1042 57.8149
80.0617 -23.5356 -17.2958 13.5375 -87.2274
-1.6445 -69.9835 -72.6382 -79.2397 -82.2557
>> edg = [-90,-67.5,-22.5,22.5,67.5,90+eps];
>> rep = [-90,-45,0,45,90,NaN];
>> [~,idx] = histc(n_rounded,edg);
>> rep(idx)
ans =
0 0 45 -45 -45
-90 -45 0 90 -45
90 90 -45 90 45
90 -45 0 0 -90
0 -90 -90 -90 -90
  5 Comments

Sign in to comment.

More Answers (1)

Matt J
Matt J on 22 Feb 2016
Edited: Matt J on 22 Feb 2016
[~,~,bins]=histcounts(n_rounded,[-90,-67.5,-22.5,22.5, 67.5,90] );
targetValues=[-90,-45,0,45,-90];
n_rouned=targetValues(bins);
  1 Comment
Ram
Ram on 22 Feb 2016
error Undefined function 'histcounts' for input arguments of type 'double'.

Sign in to comment.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!