有没有办法将mm：ss.00转换为seconds.00？

I've got some performance time data in mm:ss.00 format (i.e. 02:15.45, or 00:34.58). R is recognizing the variable as a factor, but I'd like to convert each performance time to just seconds (i.e. 02:15.45 to 135.45). I've searched for an answer but can't seem to find a way to make it work. Thanks in advance.I've got some performance time data in mm:ss.00