Converting time string to time or numeric format

I have a time column in the format of 00:00 00:30 01:00.

I want to subset to certain hours but I don't understand how to convert it to the right format

for the date i used as.date() is there someting 开发者_运维技巧similar?

i am sorry i got it i used the strptime and strftime functions like so:

strftime(strptime(x, format="%H:%M"),"%H")