尺寸数不正确，数组下标不正确

I am new to using R and thus my question might be a simple one, but nonetheless I have spent a lot of time trying to figure out what I am doing wrong and to no avail. I have discovered a lot of help on this site in the past week searching through other questions/answers (thank you!) but as someone new, it is often difficult to interpret other people's code. I am new to using R and thus my question might