Utilizing sqrt and square, "Check for incorrect argument data type or missing argument in call to function 'sqrt'"

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Casey Park 2021-9-30

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https://ww2.mathworks.cn/matlabcentral/answers/1463759-utilizing-sqrt-and-square-check-for-incorrect-argument-data-type-or-missing-argument-in-call-to-fu

编辑： Rik 2021-9-30

I am currently trying to create an expression

where Ix, and Iy are 100x100 uint8 matrixes

X = sqrt((Ix^2)+(Iy^2))

However I get "Check for incorrect argument data type or missing argument in call to function 'sqrt'"

I am wondering what is wrong here, additionally should I be using element power ".^" instead of "^"?

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VBBV 2021-9-30

编辑：VBBV 2021-9-30

you can check, if Ix and Iy have been used elsewhere in your function call /scripts for different purpose

Stephen23 2021-9-30

The SQRT function is only defined for floating point types SINGLE and DOUBLE, not for integer types:

https://www.mathworks.com/help/matlab/ref/sqrt.html#bu57a5h-2

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Answer 1

Rik 2021-9-30

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编辑：Rik 2021-9-30

As Stephen mentioned, the sqrt function expects either single or double. So you will have to convert it to either of those data types.

Additionally, you probably want to use .^ as that would make the square element-wise. If you don't, it makes more sense you want sqrtm instead.

X = sqrt(double( (Ix.^2)+(Iy.^2) ));

You could also consider hypot to do this computation.

help hypot
 HYPOT   Robust computation of the square root of the sum of squares
    C = HYPOT(A,B) returns SQRT(ABS(A).^2+ABS(B).^2) carefully computed to
    avoid underflow and overflow. A and B must have compatible sizes. In
    the simplest cases, they can be the same size or one can be a scalar.
    Two inputs have compatible sizes if, for every dimension, the dimension
    sizes of the inputs are either the same or one of them is 1.
 
    Example:
       format short e
       a = 3*[1e300 1e-300]
       b = 4*[1e300 1e-300]
       c1 = sqrt(a.^2 + b.^2)
       c2 = hypot(a,b)
 
       x = 1.271161e308
       y = hypot(x,x)
 
    Class support for inputs A, B:
       float: double, single
 
    See also ABS, NORM, SQRT.

    Documentation for hypot
       doc hypot

    Other functions named hypot

       codistributed/hypot    gpuArray/hypot    sym/hypot