Remap values of 256x256 array based on ranges

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]

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

Answer 1

[Stephen23]

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

[Ram]

 thanks for reply sir getting error 
Error using vertcat
Dimensions of matrices being concatenated are not consistent.
how to solve

[Stephen23]

"How to solve"

My answer works without error: I tested it. You are getting an error because of something you wrote, but you have not shown this to us. How am I supposed to know what you wrote if you do not show it? Sorry, but my mind-reading skills are a bit rusty, and I cannot read your computer screen, so it is difficult to diagnose what error you have in your code when you do not show us that code.

[Ram]

nice sir error resolved nice code but when opening idx from workspace it is indicatiing number wise 1,2,3,4,5 like 1 represnting -90,2 represnting -45 and so on ,how to get values in workspace by anglewise.only in command window its showing angle wise

[Stephen23]

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]

correct done sir

Answer 2

[Matt J]

 [~,~,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]

error Undefined function 'histcounts' for input arguments of type 'double'.