Hi, In Exercise 12.06 of PBOR where baby.weight is being used in Linear Regression, the code provided by ActEd & my code seems to be similar but I am not getting the answer for the same. Code by ActEd: baby <- read.table("baby weights.txt",header=TRUE) baby attach(baby) model1 <- lm(weight~gestation) coef(model1)[1]+coef(model1)[2]*33 #2.14kg #Wrap the "gestation" parameter inside a data frame newdata1 <-data.frame(gestation=33) #Then we use the "predict" function predict(model1,newdata1) #2.14kg My Code: model1 <- lm(baby.weights$weight~baby.weights$gestation) coef(model1)[1]+coef(model1)[2]*33 ## 2.141429 newdata1 <- data.frame(baby.weights$gestation = 33) The error in the above code: unexpected '=' in "newdata1 <- data.frame(baby.weights$gestation=" Now I tried the method of attaching the headers: attach(baby.weights) newdata1 <- data.frame(gestation=33) predict(model1,newdata1) ## 1 2 3 4 5 6 ## 1.528571 1.937143 2.345714 2.754286 3.162857 3.571429 Warning message: 'newdata' had 1 row but variables found have 6 rows In summary, the issue that I have been encountering is that despite having the same code as that provided by ActEd, I am not getting the answer that I should be getting i.e. in this case 2.141429. Request someone to help me out here. Regards,
Hi, So my query is basically that I am not getting a single value like the one which is being provided in the solutions but I am getting 6 values instead. Best, Naitik Shah.
The issue is the name you are using in the data.frame does not match the name used in the lm function. Hence, the predict function has no idea what to do. However, if you try to match it using: newdata1 <- data.frame(baby.weights$gestation=33) you'll still get a problem as $'s don't work in a data.frame and you end up with the same problem. So either use: weight <- baby.weights$weight gestation <- baby.weights$gestation lm(weight~gestation) or lm(weight~gestation, data=baby.weights) predict(model1,newdata1) or attach(baby.weights) lm(weight~gestation) Then all of these will work with newdata1 <- data.frame(gestation=33)
