Troubleshooting Integers in Matlab: Why Does 1019/250*250-1019 Not Result in 0?

[gerben]

Does anyone have an idea why this expression in Matlab with integers does not give zero as an answer:

>> 1019 / 250 * 250 - 1019
ans = -1.1369e-013

 

[enigma]

AFAIK, MATLAB doesn't specifically store an integer variable type.

If you need to be sure you have an integer output, use either:

fix(input)

or

floor(input)

to round it to the nearest or down to the next lowest integer.

Functions such as int2str automatically have a fix() in the command definition.

 

[tacman]

There are a few possible reasons why this expression does not result in 0. One possibility is that Matlab is using floating-point arithmetic, which means that the numbers are not being represented exactly. This can lead to small rounding errors, which can result in a non-zero answer. Another possibility is that the order of operations is causing the expression to be evaluated in a way that produces a non-zero answer. In this case, the division and multiplication would be performed first, resulting in a non-zero answer, and then the subtraction would be performed. To get a more accurate result, you could try using the "format long" command to increase the precision of the output or use the "round" function to round the answer to the nearest integer. It's also important to make sure that the numbers being used are actually integers and not stored as floating-point numbers.