"parameter {0} must be a real scalar" error when using parfor

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Kevin Sun 2022-4-1

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回答： Edric Ellis 2022-4-1

Hello,

In the following parfor loop, I want to add data into a newly created column in a mysql table by going row by row and manually inserting the data using the "update" function. But I end up getting an error, saying that the parameter isn't a scalar. I'm not sure why the error occurs since the beginning and ending values of the loop are both scalars. And if I replace "sizeOfColumn" with a literal constant, it also gives me the same error.

Thank You so much.

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Walter Roberson 2022-4-1

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I wonder if you need to use

data = newColumn(i,1);

?

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Answer 1

Edric Ellis 2022-4-1

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I think you need to use createConnectionForPool to make your database connection object and have it work correctly inside your parfor loop. (This was introduced in R2019a - if you're using an earlier release, you can probably achieve something pretty similar by using parallel.pool.Constant.)