Whenever I try to run the app.R file and change the choices from the front end this error occurs:
"ERROR: value 'NA' not found in choices
Warning: attributes are not identical across measure variables;
they will be dropped"
though I am able to achieve the expected output Internally, this error causes a problem when I try to Deploy it in the R Shiny and the results are erroneous.
We don't really have enough info to help you out. Could you ask this with a minimal REPRoducible EXample (reprex)? A reprex makes it much easier for others to understand your issue and figure out how to help.
Please have a look at this guide, to see how to create one for a shiny app