Standard deviation of aggregate data

Hi

I have two matrix with 1) day 2) travel time (sec). Where there are several observations of travel times per day. And date for more than two years.

day .......Traveltime

1 .............220

1 .............230

1 .............240

2 .............210

2 .............210

...etc

How can I aggregate the data_, so that I will have only one observation (average travel time) per day, and the standard deviation for each day.

So that the output, will be something like this:

day.......average_time.......Std_dev

1............230.............10

2............210.............0

I would appreciate if you can help me.

Answer 1

[Shashank Prasanna]

Group stats can be used to compute statistics based on some grouping. In this case day is the grouping variable and mean and standard deviation are your statistics.

Take a look at few examples that demonstrate how to do this:

http://www.mathworks.com/help/stats/grpstats.html

[Abraham]

Thank you very much Shashank