MATLAB: With and without bracket

bracket

SD = [1 2 3 4 5 6 7 8 9 10], I want to calculate the mean of SD, the two codes below gives me two answers

why bracket can make difference.

1) mean SD

2) mean (SD)

Best Answer

This statement calls the mean function using command syntax.

mean SD

This is equivalent to the following:

mean('SD')
mean(double('SD'))
mean([83 68]) % ASCII values of 'S' and 'D'

On the other hand, this statement calls the mean function using function syntax, with the variable whose name is SD as the input rather than the char array 'SD' as input.

mean(SD)

For more information about the difference between command syntax (most commonly used for functions like help, doc, hold, etc.) and function syntax see this post on Loren's blog and/or this page in the documentation.

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MATLAB: Floor function with a space giving an array output

Your example uses command syntax, which is explained here:

https://www.mathworks.com/help/matlab/matlab_prog/command-vs-function-syntax.html

The equivalent function syntax is this:

floor('[17.23]')

Because character codes do not have fractional parts, the floor operation does not change any of the character codes, so your example is exactly equivalent to simply listing the character codes themselves:

double('[17.23]')

or even just

+'[17.23]'

"Does anyone know why this is happening?"

Due to MATLAB's origin as an interactive wrapper around Fortran, and the coding fashions at the time.

"Or whether it is even meant to happen or if it is a bug?"

Command syntax has been there right from the very start of MATLAB. I recommend avoiding it.

MATLAB: Eval on multi-line strings – no return value

to expand it a bit more. what is going on with your result = eval(string) is exactly how it is written.

you're setting everything within the string into the result which doesn't compute. so in essence you're typing (which won't work)

 >> result = a=25,if (a == 30),a = 75;,else,a =42,end,37

which doesn't get you result = 37

What you could do just like you did with your fprintf statement

just do:

 sprintf('a=25\nif (a == 30)\n   a = 75;\nelse\n   a =42\nend\n37')
 eval(ans)
 result = ans

Best Answer

Related Solutions

MATLAB: Floor function with a space giving an array output

MATLAB: Eval on multi-line strings – no return value

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