Generating equations from factors in R -

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• google docs exports spreadsheet values commas. read.csv() in r treats these factors instead of numeric 2 answers

i new r, , trying create new column, 1 column minus column. example:

price <- c("$10.00", "$7.15", "$8.75", "12.00", "9.20") quantity <- c(5, 6, 7, 8, 9) price <- as.factor(price) quantity <- as.factor(quantity) df <- data.frame(price, quantity) 

in actual data set, columns imported factors. when try create new column this:

diff <- price - quantity in ops.factor(price, quantity): - not meaningful factors 

i have tried coerce data numeric using as.numeric(df), as.numeric(levels(df)), as.numeric(levels(df))[df], , setting stringsasfactors false, data gets converted nas. data.matrix changes values. there way above equation work? thanks!

you should avoid "" , $ in price column , avoid converting them factors if want math operations on them:

price <- c(10.00, 7.15, 8.75, 12.00, 9.20) quantity <- c(5, 6, 7, 8, 9) df <- data.frame(price, quantity)  df$diff <- price - quantity  df   price quantity diff 1 10.00        5 5.00 2  7.15        6 1.15 3  8.75        7 1.75 4 12.00        8 4.00 5  9.20        9 0.20