MATLAB: How to choose 2 people randomly among 12

randirandom number generator

Hi all,

Here is my question: I have a group of 12 peoples, Now I want to make a mini group by picking 2 of them by random. I've somehow done that, but the problem is that I want the result to be shown as a 2×1 vector, and not 2×2 matrix .

Here is my code:

Group={'ae','bk','cn','es','fh','hv','mh','ol','sd','sg','ss','ts'}; m=randi([1 12],2,1) % A 2×1 array of random numbers between 1 and 12 Minigroup=[Group{m(1)} ; Group{m(2)}]

As you see, size of the Minigroup is 2×2 . Any suggestions?

Thank you

Best Answer

Group={'ae','bk','cn','es','fh','hv','mh','ol','sd','sg','ss','ts'}; 
idx = randperm(12,2);
Group{idx}

I think you want to use randperm() instead of randi(), because randi() can give you the same index twice and presumably you want two different people.

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MATLAB: Find timeseries mean for 10 years

Assuming you have a vector named temperature that stores the temperatures and a vector named dt that stores the datetime stamps (in datetime format), you can use findgroups() to group the data into decades and then splitapply() to calculate the group means.

% Create demo data
dt = datetime(1950,1,1):datetime(2019,12,15);
temperature = rand(size(dt)) * 100; 
% Group by decade
[groups, groupID] = findgroups(floor(year(dt)/10)*10); 
% Compute decade means
decMeans = splitapply(@mean,temperature,groups); 
% Put results into a table
results = table(groupID.', decMeans.','VariableNames',{'Decade','MeanTemp'});

View results

results =
  7×2 table
    Decade    MeanTemp
    ______    ________
     1950      49.348 
     1960      50.959 
     1970       50.13 
     1980      49.847 
     1990      49.808 
     2000      49.471 
     2010      49.404

[update]

If there are NaN values you'd like to ignore,

decMeans = splitapply(@(x)mean(x,'omitnan'),temperature,groups);

MATLAB: Randomly grouping cells in cell array

No need for a loop.

% create 22 names of people (just letters)
names = num2cell(char(97:118));    % {'a' 'b' 'c' ... 'v'} 
number_of_people = numel(names); 
number_of_groups = 6; 
% Create random order of names
randOrder = randperm(numel(names)); 
namesPerm = names(randOrder); 
% Determine number of people per group
groupNum = floor(number_of_people / number_of_groups) + [ones(1,rem(number_of_people,number_of_groups)), zeros(1,number_of_groups - rem(number_of_people,number_of_groups))];
% Create groups
groupIdx = [0,cumsum(groupNum)]; 
nameGroups = arrayfun(@(i){namesPerm(groupIdx(i)+1:groupIdx(i+1))},1:numel(groupNum));

nameGroups is a cell array of 6 groups

nameGroups =
  1×6 cell array
    {1×4 cell}    {1×4 cell}    {1×4 cell}    {1×4 cell}    {1×3 cell}    {1×3 cell}
>>

% Convince yourself that the subgroups do not contain duplicates
% or missing names
numel(unique([nameGroups{:}]))  ==   numel(names)   %should equal 1 | true

To use your loop instead, all you need to do is switch around some of the inputs in mat2cell(). This function drives me crazy sometimes.

grouping = mat2cell(randorder(:), split, 1);
%    Make it a column vector ^^^  ^^^^^^^^ switch those two inputs

Best Answer

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MATLAB: Find timeseries mean for 10 years

MATLAB: Randomly grouping cells in cell array

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