How to pick the right month?

The data file covered 13 years from 2003-2016.

But in the data there is no date just the values of prices and demand.

So, can you help me to write a simple code to pick the date,

for example the data of march for all the years?? Then how to calculate the mean and the std for each month?

[Walter Roberson]

It would have been better if you had left the information that the data file covered 13 years from 2003: that would have provided context for other people reading the question hoping to learn from it.

Remember that we are not providing free private consulting service: we volunteer so that everyone can learn from what we say, by reading the questions and answers both.

[gjashta]

Sorry for my mistake!

Answer 1

[Walter Roberson]

Price = Data1(:,1);
Demand = Data1(:,2);
tv = (datetime([2003,1,1]):datetime([2015,12,31])).';
[Y,M,D] = ymd(tv);
DT = timetable(Price, Demand, Y, M, D, 'RowTimes', tv);

Now you can do tests such as

MarchData = DT(DT.M==3,:);

and you can also use timerange() selectors, https://www.mathworks.com/help/matlab/ref/timerange.html

and you can also do calculations such as

retime(DT, 'monthly', 'sum')

[Walter Roberson]

retime(DT(:,{'Price','Demand'}), 'monthly', 'mean')
retime(DT(:,{'Price', 'Demand'), 'montly', @std)

or

retime(DT(:,{'Price','Demand'}), 'monthly', @(v)[mean(v), std(v)])

If you are certain that your variables of interest are the first two, then you could change the indexing to DT(:,1:2)

JuneDataPD = DT(DT.M==6,{'Price','Demand'});
retime(JuneDataPD, 'monthly', @(v) [mean(v), std(v)])

[Walter Roberson]

See rmmissing()

I guess they are being added in automatically by the retime('monthly') .

There are some alternate approaches once you have selected the data, such as using findgroups() and splitapply()

[gjashta]

Thank you!

[gjashta]

How can I substract the mean of march for each year from the daily demand of march? Two vectors with defferent length.