Convert data.frame column to a vector?

I’m going to attempt to explain this without making any mistakes, but I’m betting this will attract a clarification or two in the comments. A data frame is a list. When you subset a data frame using the name of a column and [, what you’re getting is a sublist (or a sub data frame). If you want … Read more

Converting string to unsigned int returns the wrong result

You should instead use std::strtoul, found in <cstdlib>, which is designed for unsigned numbers, has a larger range, and reports errors better. If you want to use std::string for input and exceptions for error handling, use std::stoul. A short, highly efficient implementation would be as follows: This will be much faster than istringstream, culture-invariant (so no unexpected changes to behavior when … Read more

How can I convert a string to a float in mysql?

It turns out I was just missing DECIMAL on the CAST() description: DECIMAL[(M[,D])] Converts a value to DECIMAL data type. The optional arguments M and D specify the precision (M specifies the total number of digits) and the scale (D specifies the number of digits after the decimal point) of the decimal value. The default … Read more

Converting from byte to int in Java

Your array is of byte primitives, but you’re trying to call a method on them. You don’t need to do anything explicit to convert a byte to an int, just: …since it’s not a downcast. Note that the default behavior of byte-to-int conversion is to preserve the sign of the value (remember byte is a … Read more