Cell Function

3 views (last 30 days)
James
James on 3 Oct 2011
I've created a sliding window using the cell function. I used this as I am creating the sliding window for a daily time series of data over a few hundred years. The sliding window is 30 years long and because of leap years each row is a different length. So I now have an array of data that looks like this:
data =
10957x1 double
10957x1 double
10958x1 double
and so on...
I'm unfamiliar with the cell function however as this code was shown to me. How do I now use the data in this series? Whenever I type the command for example:
data (1,1)= 10957x1 double
But I need to do a number of things such as take the mean of each vector in the array, how do I do this?

Accepted Answer

Wayne King
Wayne King on 3 Oct 2011
x = {randn(1000,1), randn(1000,1), randn(1000,1)};
meanz = cellfun(@mean,x,'UniformOutput',false);
meanz = cell2mat(meanz);
  5 Comments
Wayne King
Wayne King on 3 Oct 2011
you can use cellfun to do that.
Jan
Jan on 3 Oct 2011
@James: Use curly braces to access cell elements:
for 1:n, mean(data{n,1}), end
for 1:n, detrend(data{n,1}), end

Sign in to comment.

More Answers (5)

Andrei Bobrov
Andrei Bobrov on 3 Oct 2011
data2 = cellfun(@(x){mean(x) detrend(x)},x,'un',0)
ADD
data2 = cellfun(@(x)[mean(x);detrend(x)],x,'un',0)
datadouble = [data2{:}];
datamean = datadouble(1,:)
datadetrend = datadouble(2:end,:);
  1 Comment
James
James on 3 Oct 2011
This just gives me the same problem?
It still outputs it as a cell array, I cant do anything with a vector where all it shows me is:
1x2 double, for every row
How can I extract the data from this as it is not currently usable?
I need to plot graphs of this data using many different functions, not just the ones I've put on here.

Sign in to comment.


Wayne King
Wayne King on 3 Oct 2011
You can use two calls to cellfun and then use cell2mat
data1 = cellfun(@mean,x,'UniformOutput',false);
data1 = cell2mat(data1);
data2 = cellfun(@detrend,x,'UniformOutput',false);
data2 = cell2mat(data2);
  2 Comments
Wayne King
Wayne King on 3 Oct 2011
Notice that data2 contains the detrended data as column vectors, which you can plot()
plot(data2)
data1 is a row vector of means
James
James on 3 Oct 2011
Detrend outputs a new value for each value I have. So at the moment using cell2mat the function just seems to put all 30 year period into one single column. Is there a way to define where the data goes? I have tried this but it doesn't seem to work?
detrendcell = cellfun(@(T32)detrend(T32,'linear'),T32,'un',0);
% detrends the data in each cell
n = numel(detrendcell);
for i=1:n
detrendT(i) = cell2mat(detrendcell(i));
end

Sign in to comment.


Fangjun Jiang
Fangjun Jiang on 3 Oct 2011
Since data is a cell array, you need to use {} to reference its element, like data{1}, data{2}, data{3}, etc.
data{1} will be a 10957x1 double array, to reference its element, use data{1}(1), data{1}(100), data{1}(10957), etc.

James
James on 3 Oct 2011
%%Data Loading
close all
clear all
cet = load ('cet_1772_2009.asc', '-ascii'); % Loads CET from asc file.
year = cet(:,1);
temp = cet(:,4);
day = cet(:,3);
month = cet(:,2);
% Loads Data from CET asc file and sets vectors
%%Constants and vectors
dates = datenum([year,month,day]);
%%30 Year Periods
StartYear=1772;
EndYear=2009;
Period=30;
T32=cell(EndYear-StartYear-Period+1,1);
for Year=StartYear:(EndYear-Period)
StartCount=datenum(Year,1,1)-datenum(StartYear,1,1)+1;
DataCount=datenum(Year+Period,12,31)-datenum(Year,12,31);
T32{Year-StartYear+1}=temp(StartCount:(StartCount+DataCount),1);
end
%%Detrend, mean etc
meancell = cellfun(@(T32)mean(T32),T32,'un',0);
meanT = cell2mat(meancell);
detrendcell = cellfun(@(T32)detrend(T32,'linear'),T32,'un',0);
n = numel(detrendcell);
for i=1:n
n1 = numel(detrendcell{i});
detrendT(:,i) = cell2mat(detrendcell{i}(1:n1));
end
  2 Comments
James
James on 3 Oct 2011
This is my code and it outputs the error:
??? Cell contents reference from a non-cell array object.
Error in ==> cell2mat at 43
cellclass = class(c{1});
Error in ==> Untitled2 at 63
detrendT(:,i) = cell2mat(detrendcell{i}(1:n1));
Any idea whats wrong with it?
Fangjun Jiang
Fangjun Jiang on 3 Oct 2011
Why need meancell = cellfun(@(T32)mean(T32),T32,'un',0)
Can it be meancell = cellfun(@mean,T32,'un',0)

Sign in to comment.


Wayne King
Wayne King on 3 Oct 2011
Why didn't you do what I suggested?
detrendcell = cellfun(@(T32)detrend(T32,'linear'),T32,'un',0);
detrendcell = cell2mat(detrendcell);
By the way, 'linear' is the default option for detrend:
so
detrendcell = cellfun(@detrend,T32,'UniformOutput',false);
detrendcell = cell2mat(detrendcell);
The above returns a matrix whose columns are your detrended series.
Is the same and a bit cleaner.
  5 Comments
Wayne King
Wayne King on 3 Oct 2011
Transpose your input
T32 = T32';
detrendcell = cellfun(@detrend,T32,'UniformOutput',false);
detrendcell = cell2mat(detrendcell);
James
James on 3 Oct 2011
This returns the error:
??? Error using ==> cat
CAT arguments dimensions are not consistent.
Error in ==> cell2mat at 77
m{n} = cat(2,c{n,:});
Error in ==> Untitled2 at 28
detrendcell = cell2mat(detrendcell)

Sign in to comment.

Categories

Find more on Data Type Identification in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!