How to define a variable as an integer that's equal to or greater than zero?

I have the following if statements:

if struct_idx == 1 + 4*n % where n is an integer equal to or greater than zero
            measurement_data(struct_idx).unit = 'SD1';
elseif struct_idx == 2 + 4*n % where n is an integer equal to or greater than zero
            measurement_data(struct_idx).unit = 'SD2';
elseif struct_idx == 3 + 4*n % where n is an integer equal to or greater than zero
            measurement_data(struct_idx).unit = 'SD3';
else struct_idx == 4 + 4*n % where n is an integer equal to or greater than zero
            measurement_data(struct_idx).unit = 'SD4';
end

How can I turn the commented parts into working code?

Answer 1

[Torsten]

rest = mod(struct_idx,4);
if rest == 1
  ...
elseif rest == 2
  ...
elseif rest == 3
  ...
elseif rest == 0
  ...
end

[Steven Lord]

Since you only have a small finite list of possible values for rest (assuming struct_idx is a real finite scalar) you could also use a switch statement.

Alternately, given the specific details of the user's code, just use rest directly without any if / elseif / end or switch statement.

rest = mod(struct_idx, 4);
rest(rest == 0) = 4;
unit = "SD" + rest; % If using a string is acceptable
unit = ['SD' num2str(rest)] % if rest is a scalar and you need a char vector

Answer 2

[Fangjun Jiang]

rem(struct_idx,4)==1