using predict() and table() in r

Question

I have used glm on the learning data set which without NAs has 49511 observations.

glmodel<-glm(RESULT ~ ., family=binomial,data=learnfram)

Using that glm, I tried to predict the probability for the test data set which has 49943 without NAs. My resulting prediction has only 49511 elements.

predct<-predict(glmodel, type="response", data=testfram)

Why is it that the result of predict is not for 49511 elements?

I want to look for false positives and false negatives. I used table, but it is throwing error:

table(testfram$RESULT, predct>0.02)
## Error in table(testfram$RESULT, predct> 0.02) : 
##  all arguments must have the same length

How can I get my desired result?

Answer 1

You used the wrong parameter name in predict. It should be newdata=, not data=. So the reason you get 49511 elements is that the default for predict when you don't specify new data is to output the predicted values for the data you created the model with. Hence you're getting the predicted values for your original data.