MATLAB Answers

Data types of arrays in a function

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Samuel Katongole
Samuel Katongole on 6 Jul 2020
Edited: Stephen Cobeldick on 7 Jul 2020
Hey,
I am trying to create a function that takes an array as an input arg and returns another array as output arg which should be if all elements of the input array are within the range of int8 is an int8, otherwise, it is the same type as the input array...The function is called as B=safe_int8(A).
I am using the following loop....
B=zeros(size(A)); % Pre-allocation since B changes size
for ii=1:size(A,1)
for jj=1:size(A,2)
if -128<A(ii,jj)&& A(ii,jj)<127
A=int8(A);
B=A;
else
B=(A);
end
end
end
Running it yields for instance
>> A=[1 0 3;4 5 6];
>> B=safe_int8(A)
B =
2×3 int8 matrix
1 0 3
4 5 6
>> A=[1 0 345;4 5 6];
>> B=safe_int8(A)
B =
2×3 int8 matrix
1 0 127
4 5 6
>> A=[1 1.05 3;4 5 6];
>> B=safe_int8(A)
B =
2×3 int8 matrix
1 1 3
4 5 6
Of course, the first trial gives the right answer; but the second and third which should give the class for B as double are instead returning it as an int8...How do i correct this?

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Answers (2)

madhan ravi
madhan ravi on 6 Jul 2020
if all((-128<=A)& (A<=127))
A=int8(A);
B=A;
else
B=(A);
end
Loops are not necessary here.

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Stephen Cobeldick
Stephen Cobeldick on 7 Jul 2020
Edited: Stephen Cobeldick on 7 Jul 2020
B = int8(A);
if any(B(:)~=A(:))
B = A;
end
Note that this is a more versatile approach because it does not use hard-coded values, i.e. you can trivially change only the type conversion function and it will work. The type conversion function could even be a function handle.

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