make our own signum

Question

Soveatin Kuntur 2021-5-11

回答： Walter Roberson 2021-5-11

Dear all,

is there any simple way to transform this javascript logic:

return value < 0 ? -1 : 1

into matlab

Answer 1

Walter Roberson 2021-5-11

Under the interpretation that nan values are not less than 0 (they are not greater than 0 either)

output = (value < 0) .* -2 + 1;
output(isnan(value)) = 1;

or

output = (value < 0) .* -1 + (value >= 0) .* 1
output(isnan(value)) = 1;

or

output = (value >= 0) - (value < 0);
output(isnan(value)) = 1;

or

output = sign(value) + (value == 0);
output(isnan(value)) = 1;

If you are certain that the values will never be NaN then you can simplify the code.