Error in as.data.frame(newdata) : object 'newdat' not found

This error message suggests that the R code is trying to convert an object named "newdat" into a data frame using the function "as.data.frame()", but R cannot find the object "newdat".

Possible reasons for this error include:

1. The object "newdat" was not created or assigned properly earlier in the code, and thus it does not exist in the R environment.

2. The object "newdat" was created outside the current R session or in a different function, and thus it is not accessible to the current code.

3. There is a typo in the code, and the object name should be "newdata" instead of "newdat".

To troubleshoot this error, you can check the previous code lines to see if "newdat" was created or assigned properly. You can also use the "ls()" function to list all the objects in the current R environment and see if "newdat" is listed. Finally, you can check if there is a typo in the code and correct it if necessary.