Error object df13 not found

This error message indicates that R cannot find an object named "df13". This could be due to several reasons, such as:

1. The object was not created or loaded into the R environment.
2. The object was created or loaded but was accidentally deleted or overwritten.
3. The object was created or loaded in a different R session or workspace.

To resolve this error, you can try the following steps:

1. Check if you have created or loaded the object correctly. Make sure that the object name is spelled correctly and that it exists in your current R session or workspace.
2. If you have accidentally deleted or overwritten the object, you can try to recreate or reload it from a saved file or data source.
3. If the object was created or loaded in a different R session or workspace, you can try to load it into your current session using the "load" function or by copying the code that created the object