Hi professor Wise, The sample1.xslx could not be accessed on my device, and got a warn "The specified resource was not found or you do not have permission to access it." I am not sure is there any problem with this file. Also, as the Ass2 says: "contents of the input files may change", I am concerning that should we assume that all the value in the input file is under the reasonable format, for example, there would not have an invalid value like "2@20" in years so that we need to handle this error. Best regards. Zhiyang

"Zhiyang Xu" <23*5*0*2@s*u*e*t*u*a*e*u*a*> wrote: Hi Zhiyang, Sample1.tsv is just the first two countries round in Sample2.tsv (with the other two not have enough data-points). I have now made that explicit, but also provided Sample1.tsv, to avoid further confusion. Yes, cells may be empty, but if they have values, those values are of the appropriate type: numbers were numbers are expected, strings where strings are expected. That said, it is always a good idea to eye-ball the data and look for odd entries, e.g. Unicode characters. You can do this using the version of the cat command: cat -vet (Yes, taking my unhappy cat to the vet is how I remember this one 😀) Cheers MichaelW 👨‍🎨