MATLAB: How to count date occurrence independently of year

date dates datenum plot occurrenceMATLAB

Hi,
I have an excel file with about 6000 dates from year 1900 and until now. I want to plot the occurrence of dates irrespective of year to see if the occurrence is dependent of time of year. How can I do this? The excel file is attached.

Best Answer

This solution creates a table (T) that lists all month-day combinations in your data in 1 column and the count in the 2nd column. It also produces a plot showing the frequency of month-day combinations (ignore the year label). See comments for details. 
% Read in the dates as datetime
m = readmatrix('Dates.xlsx','OutputType','datetime'); 
% Remove missing vals and sort dates 
% (sort isn't really needed but makes it easier to look at the vector)
m = sort(m(~isnat(m))); 
% find day-of-year number
doy = day(m,'dayofyear'); 
% count number of doy's
binEdges = 0:1:max(doy); 
mdCount = histcounts(doy,binEdges); 
% list all possible [month,day] values (we'll use them as labels)
allPossibleDates = (min(m):max(m)).'; 
mdAllPossible = unique([month(allPossibleDates), day(allPossibleDates)], 'rows'); 
allPossible = datetime(1904,mdAllPossible(:,1),mdAllPossible(:,2),'Format', 'MM/dd'); % Year must be any leap year
% Put results in summary table
T = table(allPossible(:), mdCount(:),'VariableNames', {'MonthDay', 'count'}); 
figure(); 
axh = axes(); 
plot(axh, T.MonthDay,T.count)
axh.XAxis.TickLabelFormat = 'MM-dd'; %reformat x ticks if you want mm/dd
xlabel('Day of year (mm-dd)')
ylabel('Count')
title(sprintf('Data from %s to %s',datestr(min(m),'mm/dd/yyyy'),datestr(max(m),'mm/dd/yyyy')))
Result:
head(T)   % show the first few rows of table
ans = 
  8×2 table
    MonthDay    count
    ________    _____
     01/01        0  
     01/02       34  
     01/03       34  
     01/04       24  
     01/05       24  
     01/06       27  
     01/07       13  
     01/08       32
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