How is the division of two numbers carried out in Matlab?

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PE 2018-3-23

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评论： PE 2018-3-23

The behavior is as expected when both the denominator and the numerator are in 'double' precision. If either of the two are integer, as in the example below, the rounding error yields unexpected division results.

double(475904) / double(512) = 929.5

int32(475904) / int32(512) = 930

int32(475904) / double(512) = 930

double(475904) / int32(512) = 930

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Stephen23 2018-3-23

编辑：Stephen23 2018-3-23

The documentation that David Fletcher refers to are these:

https://www.mathworks.com/help/matlab/matlab_prog/integers.html

https://www.mathworks.com/help/matlab/numeric-types.html

PE 2018-3-23

Thanks. Here are two not so obvious learnings in Matlab- 1) Data operations that involve both integers result in an integer data type. 2) The division of two integers is rounded to nearest integer by default. If at all one would have to do this operation, idivide( int32(475904), int32(512) ) would be used.

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Answer 1

John D'Errico 2018-3-23

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编辑：John D'Errico 2018-3-23

在 MATLAB Online 中打开

Think about what the class of the result is. If you don't know how to use the class function to check that, then learn to read the output of the whos command. (In fact, in newer MATLAB releases, just displaying a variable at the command line tells you the class, if it is not a double.)

Then consider if the result is stored in an integer variable, then why would you expect a non-integer result? That is, an int32 cannot represent non-integers. So MATLAB stores only the integer part, essentially rounding to the nearest integer.

double(4) / int32(3)
ans =
  int32
   1
double(5) / int32(3)
ans =
  int32
   2

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PE 2018-3-23

Thanks! This wasn't intuitive given the experience of other languages. But it seems it is clearly documented in Matlab Fundamentals. Thanks for the reference link.

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