# Remap values of 256x256 array based on ranges

3 views (last 30 days)
Ram on 22 Feb 2016
Commented: Ram on 22 Feb 2016
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.
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

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
Stephen23 on 22 Feb 2016
If it is showing in the command window then it is also in your workspace. Your request is not totally clear to me, but I think you might just need to allocate the output to a variable:
out = rep(idx);
Ram on 22 Feb 2016
correct done sir

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);
Ram on 22 Feb 2016
error Undefined function 'histcounts' for input arguments of type 'double'.