Find timeseries mean for 10 years

Hi,

I have time-series temperature data for years 1950 to 2010.

I want to calculate the decadal means i.e. 1950 - 1960, 1960 - 1970 etc and plot them as a histogram

What code should I use to calculate the 10 year means?

Thank you.

Answer 1

[Adam Danz]

Assuming you have a vector named temperature that stores the temperatures and a vector named dt that stores the datetime stamps (in datetime format), you can use findgroups() to group the data into decades and then splitapply() to calculate the group means.

% Create demo data
dt = datetime(1950,1,1):datetime(2019,12,15);
temperature = rand(size(dt)) * 100; 

% Group by decade
[groups, groupID] = findgroups(floor(year(dt)/10)*10); 
% Compute decade means
decMeans = splitapply(@mean,temperature,groups); 
% Put results into a table
results = table(groupID.', decMeans.','VariableNames',{'Decade','MeanTemp'});

View results

results =

  7×2 table

    Decade    MeanTemp
    ______    ________

     1950      49.348 
     1960      50.959 
     1970       50.13 
     1980      49.847 
     1990      49.808 
     2000      49.471 
     2010      49.404 

[update]

If there are NaN values you'd like to ignore,

decMeans = splitapply(@(x)mean(x,'omitnan'),temperature,groups);

[Sarah Yun]

Hello,

What if the data is listed in years already? (there is no month value for the 'year' function below to assign 1, 2, 3, etc)?

i.e.

1978

1979

1980

1801

How should I change the code to make it work for single year increases?

dt = Year; % yearly increments

% How should the next line change for only yearly increases - no months?
[groups, groupID] = findgroups(floor(year(dt)/10)*10); 
% Compute decade means and ignore NAN values
decMeans = splitapply(@(x)mean(x,'omitnan'),Precip,groups);
% Display results as a table
results = table(groupID.', decMeans.','VariableNames',{'Decade','MeanTemp'});

Thank you.

[Adam Danz]

If your timestamps are years in a variable named 'y', and you want averages for every 10 years,

[groups, groupID] = findgroups(floor(y/10)*10); 

and then you can use the rest of my answer.

If you want averages for every year,

[groups, groupID] = findgroups(y); 

[Sarah Yun]

Hi,

Thank you.

Now I want to run ANOVA test between the decade means

There are 9 decades, from 1900 to 2000 i.e. 1900 - 1910 etc and 9 mean values for each decade

I want to test for significance between these decades

I want to plot results (and p-values) on a histogram

How can I do this (I am a beginner, so nothing too complicated).

Thank you.

[Adam Danz]

If you'd like to perform a 1-way analysis of variance between the temperatures grouped by decade, continuing from my answer above,

p = anova1(temperature(:),groups(:));

[Sarah Yun]

Thank you.

How do I find the p-values?

It shows a box-plot only.

[Adam Danz]

Did you look at the p output?

Here's more info

https://www.mathworks.com/help/stats/anova1.html