Plotting data from a table

I have a .csv file that has temperature data of the United Kingdom from year 1912 to 2012. I have plotted the year vs. the average temperature (provided in the last column of the table) and that looks great. I now want to find the sum of each row and divide it by 12 to get the mean of every year. I don't know why it is different from the average in the table, but that is not important. I just need to find the mean of the 12 months for each year and use those as my new y-values. How can I do that as simply as possible? I have attached a photo of part of the table (watch out for the headings and the years!), a photo of the first plot that I got (blue plot) and a photo of my goal which is plotting both the blue (which I already did) and this new red "mean value" plot.

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Answer 1

[Eric Lin]

See Find the Average Across Each Row