Data format and running Mann Kendall

[Orionm45]

I have made a csv file below for chemical readings

Headers are:
Site, date (##/##/###), Value

Information is:
Site is the same (for now, eg F1), Date is one sample per month, value is anything from 0 to 30

For now im only looking at one years worth of data. I need a guide to get the data in the correct table format and codes needed to get the data into R studio.

The next problem im having is running Mann Kendal test of the data and viewing the results. Iv been trying for a couple of days now with no joy.

Any help would be great

R version 3.6.3 (2020-02-29)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

[DavoWW]

Hi @Orionm45,
Welcome to the RStudio Community Forum.
Here is a minimal reproducible example (MRE) to get you started. Just cut-and-paste this code into a new R script file which you open in RStudio, and then run it. Of course, your data will be coming from your .CSV file (see help(read.csv) for examples):

a <- "
site, my_date, value
F1, 01/01/2019, 13
F1, 01/02/2019, 16
F1, 01/03/2019, 14
F1, 01/04/2019, 18
F1, 01/05/2019, 23
F1, 01/06/2019, 21
F1, 01/07/2019, 22
F1, 01/08/2019, 25
F1, 01/09/2019, 26
F1, 01/10/2019, 26
F1, 01/11/2019, 29
F1, 01/12/2019, 30
"

in.df <- read.csv(text=a, header=TRUE, stringsAsFactors=FALSE)
in.df$my_date <- as.Date(in.df$my_date, format="%d/%m/%Y")
str(in.df)
plot(value ~ my_date, type="b", data=in.df)
lines(lowess(in.df$my_date, in.df$value))

library(Kendall)
MannKendall(in.df$value)

In future, if you provide a MRE you are much more likely to get help from forums such as this.
HTH

p.s. Try to avoid using the '#' symbol in data files - it signifies a 'comment' in R and will cause you problems.

[Orionm45]

Hi @DavoWW

Thank you so much for the reply. I am relatively new to R so still finding my feet.

From using your reply i was able to obtain a result.

Just as a learning curve would you be able to explain a few things. When i paste your code into R i receive the following errors. ""Test is the name of my file""

Test(<- read.csv(text=a, header=TRUE, stringsAsFactors=FALSE)
Error in textConnection(text, encoding = "UTF-8") : object 'a' not found

Test$my_date <- as.Date(Test$my_date, format="%d/%m/%Y")
Is this code simply to ensure all dates in formatted to the above?

My next question is im also trying to perform this on a full data set with different sites and years. Is there a way to tell R to give me the results for Mann Kendall test for each site for all years or each sites per year?

Thank you in advance

Orionm45