Does R have an equivalent for Matlab's cell array?
On Dec 22, 2012, at 2:58 AM, Matthijs Daelman wrote:
Hi I have a time series of measurements: every 10 min. a value was logged. The data look like: 20100914 08:01 3.74 20100914 08:11 3.74 20100914 08:21 3.71 20100914 08:31 4.39 20100914 08:41 3.74 This data spans several months. I would like to group the data per day. In Matlab it is fairly easy to obtain a cell array, of which the first column contains the date of each day, and the second column contains a vector, that in its turn contains all values for the corresponding day. That looks like 14-9-2010 [3.74 3.74 3.71 4.39 3.74...] 15-9-2010 [...] and so on. Is it possible to create a similar data structure in in R? I was thinking of a data frame, similar to the Matlab's cell array, but it doesn't look like data frames can contain vectors.
That's a surprising conclusion. Vectors are typical components of dataframes.
Something like a two dimensional list would do the trick, I believe, but does that exist?
A dataframe _is_ a two-dimensional list. You should probably explain what you are trying to do, since there is very possibly a better way of structuring this problem without recasting the data into a "wide format". Most of the data processing in R is handled very well without such a strategy. If you wanted to proceed despite my misgivings, then there are several functions such as `split`, `tapply` and `by` that could allow you to segregate such data. It's best to use dput to present the data since console output is often ambiguous as to the underlying data structures.