Hi Clara,
The ERR:INVALID DIMENSION error message may occur if you are trying to graph a function that does not involve the stat plot features. The error can be corrected by turning off the stat plots. To turn the stat plots off, press y , and then select 4:PlotsOff.
You specified a list dimension as something other than an integer between 1 and 999.
You specified a matrix dimension as something other than an integer between 1 and 99.
You attempted to invert a matrix that is not square.