how to obtain values using a key in another table?

I have a bit of a problem so I have my data like this:

date Concentration.

'4/13/1994' 8

'4/14/1994' 8.5

'4/15/1994' 8.3

'4/16/1994' 7.9

'4/17/1994' 8

'4/18/1994' 9.5

'4/19/1994' 9.6

'4/20/1994' 9.1

'4/21/1994' 9

'4/22/1994' 9.6

and another table with key dates data

'4/15/1994'

'4/21/1994'

what would you recommend for me to use so that i can read the dates in the first column using the second column as a key, and get an average of the data between these two dates.

I would really appreacite your recommendations.

Best

[Guillaume]

What output do you want? The average concentration between 4/15/1994 and 4/21/1994 (bounds included?) or something else?

What if the key date table has more than two rows. Is the window between each consecutive row, or is it between each two pairs of consecutive rows, e.g with:

keydates
4/15/1994
4/21/1994
4/28/1994
5/02/1994

are the windows 15:21, 21:28, 28:02 or are they just 15:21, 28:02 ?

Also can you confirm that your dates are stored as datetime?

[Esteban Tamayo]

Thank you for your response.

the windows are 15:21, 21:28, 28:02, so far the dates are not as datetime, they are strings

Thank you !

Answer 1

[Guillaume]

First, convert the date strings into proper dates. However you imported that data, you should be able to import it directly as datetime.

After the fact,

yourtable.Date = datetime(yourtable.Date, 'InputFormat', 'M/d/yyyy')  %taking a guess at your format.

Then, convert the concenration table to timetable (in recent versions of matlab you could import directly as timetable)

tt_concentration = table2timetable(yourconcentrationtable);

Then retime it according to the time vector specified in the key date table. (the dates must be uniques, ordered, and converted to datetime):

concentration_keydates = retime(tt_concentration, keydates.Date, 'mean')

[Esteban Tamayo]

Thank you for your time and answer I will try to do this.

Thank you !

[Steven Lord]

The timerange function may also be of use to you in extracting data from your timetable.