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error with sqrt in Matlab

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EDISON TOAPANTA IZA
EDISON TOAPANTA IZA on 11 Dec 2020
Commented: Steven Lord on 14 Dec 2020
hi, help please when I put this formula GEH2= sqrt(2*int64((flujo_sim2-FlujoReal2)^2)/int64(flujo_sim2+FlujoReal2)) in matlab, this returns me the following error: Check for missing argument or incorrect argument data type in call to function 'sqrt'.
why does this error give me?

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Answers (3)

Steven Lord
Steven Lord on 11 Dec 2020
The sqrt function is not defined for variables of the int64 data type. The square root of an integer value is not necessarily itself an integer value. If it were defined, what exactly would you expect x to be in the following code?
five = int64(5)
five = int64 5
x = sqrt(five)
Check for missing argument or incorrect argument data type in call to function 'sqrt'.

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Steven Lord
Steven Lord on 11 Dec 2020
Can you show the output of the following command executed immediately before the line where you define FGEH?
whos flujo_sim2 FlujoReal2
I suspect one or both of those variables are int64. If so the results of all that arithmetic is again an int64 array and sqrt is not defined for int64 arrays.
EDISON TOAPANTA IZA
EDISON TOAPANTA IZA on 14 Dec 2020
Hi, of course.
flujo_sim2=datapoint2.get('AttValue', 'Vehs(Current, Total, All)'); %give me value the software external (simulation)
FlujoReal2 =(flujo_med233 + flujo_med234 + flujo_med235); %gives me the total field value (real life) obtained from an excel table.
Steven Lord
Steven Lord on 14 Dec 2020
The lines of code you posted doesn't tell me the class of the variables, which is the important information.
But I repeat my previous question. If you have an int64 number that is not a perfect square, would you be okay with getting an answer that when squared does not give you back the original number?
sqrtDouble = sqrt(5)
sqrtDouble = 2.2361
sqrtInt = int64(sqrt(5))
sqrtInt = int64 2
sqrtDouble.^2 - 5 % close to 0
ans = 8.8818e-16
sqrtInt.^2 - 5 % not really close to 0
ans = int64 -1

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Théophane Dimier
Théophane Dimier on 11 Dec 2020
Hi, sqrt does not accept int64 as input. If you want to round the quantity first, use round, ceil or floor functions instead

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David Hill
David Hill on 11 Dec 2020
Cannot take sqrt of int64 data type. Take sqrt of double then round and convert to int64.

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