Calculate statistical parameters from certain rows of a matrix

I have data of days and temperature in specific intervals recorded through out that particular day: eg

Day Temp

1 24

1 24.5

1 24.5

2 25

2 25

2 25

3 25.5

3 25.5

3 25.5

and so on for many number of days through. If I want to take the mean of all the temperature values from only day 1, how would I go about doing this using indexing?

Answer 1

[madhan ravi]

Wanted=splitapply(@mean,x(:,2),findgroups(x(:,1))) % x(:,1) is Day and x(:,2) is Temperature
% or if you're using version prior to 2015b then:
Wanted=accumarray(Day,Temperature,[],@mean);

For only one day it’s simply:

day = 1;
mean(Temperature(Day==day))

[BoIs]

Works perfectly! Thank you

Answer 2

[Jos (10584)]

help grpstats
help accumarray