search for: thermsperday

...l data on my house.] 'days' is number of days in bill, 'temp' is average temperature in Fahrenheit. I'd like to see if there is a relationship between the gas burned (therms) and the number of heating degree days. I compute therms per day and heating degree days like this: > thermsperday <- w[,2]/w[,7] > hdd <- (w[,6] -65)*w[,7] However, I only want the data for the months in which the average temperature is less than 65 (otherwise, it's a cooling degree day). I tried ifelse, but couldn't get it to work. What simple technique am I overlooking? Thanks so much for...