Question

The following example resembles a similar problem that I’m dealing with, although the code below is merely an example, it is structured in the same format as my actual data set.

clear all

England = struct('AirT',rand(320,1),'SolRad',rand(320,1),'Rain',rand(320,1));
Wales = struct('AirT',rand(320,1),'SolRad',rand(320,1),'Rain',rand(320,1));
Ireland = struct('AirT',rand(320,1),'SolRad',rand(320,1),'Rain',rand(320,1));
Scotland = struct('AirT',rand(320,1),'SolRad',rand(320,1),'Rain',rand(320,1));

Location = struct('England',England,'Wales', Wales, 'Ireland',Ireland,'Scotland',Scotland);

FieldName={'England','Wales','Scotland','Ireland'};
Data = {England.AirT,Wales.AirT,Scotland.AirT,Ireland.AirT};
Data = [FieldName;Data];
Data = struct(Data{:});
Data = cell2mat(struct2cell(Data)');
[R,P] = corrcoef(Data,'rows','pairwise');
R_Value= [FieldName(nchoosek(1:size(R,1),2)) num2cell(nonzeros(tril(R,-1)))];

So, this script would show the correlation between pairs of Air Temperature of 4 locations. I’m looking for a way of also looking at the correlation between ‘SolRad’ and ‘Rain’ between the locations (same process as for AirT) or any variables denoted in the structure. I could do this by replacing the inputs into ‘Data’ but this seems rather long winded especially when involving many different variables. Any ideas on how to do this? I’ve tried using a loop but it seems harder than I though to try and get the data into the same format as the example.

Answer 1

Let’s see if this helps, or is what you are thinking:

clear all

England = struct('AirT',rand(320,1),'SolRad',rand(320,1),'Rain',rand(320,1));
Wales = struct('AirT',rand(320,1),'SolRad',rand(320,1),'Rain',rand(320,1));
Ireland = struct('AirT',rand(320,1),'SolRad',rand(320,1),'Rain',rand(320,1));
Scotland = struct('AirT',rand(320,1),'SolRad',rand(320,1),'Rain',rand(320,1));

Location = struct('England',England,'Wales', Wales, 'Ireland',Ireland,'Scotland',Scotland);

% get all the location fields
FieldName = transpose(fieldnames(Location));
% get the variables recorded at the first location
CorrData = fieldnames(Location.(FieldName{1}));
% get variables which were stored at all locations(just to be safe,
% we know that they are all the same)
for ii=2:length(FieldName)
  CorrData = intersect(CorrData,fieldnames(Location.(FieldName{ii})));
end

% process each variable that was recorded
for ii=1:length(CorrData)
  Data = cell(1,length(FieldName));
  % get the variable data from each location and store in Data
  for jj=1:length(FieldName)
    Data{jj} = Location.(FieldName{jj}).(CorrData{ii});
  end
  % process the data
  Data = [FieldName;Data];
  Data = struct(Data{:});
  Data = cell2mat(struct2cell(Data)');
  [R,P] = corrcoef(Data,'rows','pairwise');
  R_Value= [FieldName(nchoosek(1:size(R,1),2)) num2cell(nonzeros(tril(R,-1)))];
  % display the data, sounds good right?
  fprintf(1,'Correlation for %s\n',CorrData{ii});
  for jj=1:size(R_Value,1)
    fprintf(1,'%s\t%s\t%f\n',R_Value{jj,1},R_Value{jj,2},R_Value{jj,3});
  end
end

Let me know if I misunderstood, or if this is more involved than what you were thinking. Thanks!