I am a beginner in R and I have already worked in a file and tried around. Now I closed the file, reopened it completely and loaded it into RStudio. Strangely, I can no longer access the contents of the file.
For example, if I want to select the columns:
Test <- AfterVisits2-BeforeVisits2
Error: object 'AfterVisits20' not found
I used the "Import Dataset", the file is even loading but for some reason when I use the upper command it shows the object was not found.
Although it worked in my attempts before and the column exists in the file.
I also paid attention to the upper and lower case!
I've been trying for an hour, I'm grateful for any support!
Edit: I also tried with another file, that doesn't work either.