如何在R中改变对定量的分类响应？

Question

我有一个数据表，其中包含男性和女性的列，以及一个有和没有响应的数据表，我只需要将这些更改为0和1值，我该如何处理？

Answer 1

I doubt that you really do need to do this but here's how (assuming they are factors):

numMF <- as.numeric(MFfac) -1 # will be 0 for F and 1 for M in the usual sorting of factor levels

If they are really character vectors, then wrap factor around the MFfac that I assumed was a factor. Or:

numMF <- match(MFvec, c("Female", "Male") ) -1

 match( c("Female","Male", "Female"),  c("Female", "Male") )
[1] 1 2 1

The match function is an important resource for data conversions.

Answer 2

You can coerce a factor directly to a numeric vector: as.numeric(factor(x)) . If the default level ordering is not to your liking, specify the levels explicitly with the "levels" argument to "factor".

Answer 3

The general way to convert factors to indicator variables is using the model.matrix function. But most of the time you don't need to do this because the modeling functions (such as lm ) will call model.matrix for you.