I'm trying to run a Mann-Kendall test using a data set I have..I'm struggling with code as I keep getting an error (Input vector must contain at least three values).

What I'm trying to do is to run a Mann-Kendall test for these two variables - Year, Age groups - I'm charting the incidence of colo-rectal cancer per 100,000 population for each individual age group.

I have so far run the following commands on R after uploading my dataset

library(modifiedmk)

mkttest(I 35-39)

I 35-39 is the column, incidence in the 35 to 39 year olds. Could the error lie in the fact that the data hasnt originally been rounded up uniformly on the excel sheet. for e.g. I have 5.0292 (incidence for year 1993) in one box and 5.23 (incidence for year 2004) in the other