MATLAB: How to create a matrix, table or a cell where in odd columns variables from matrix A and in even columns variabls from matrix B will be stored

cell arraysmatricestables

For instance, I have two matrices A = ones(5,24) and B = zeros(5,24), I need to create a matrix 'C', where the first column of 'C' will consist of elements of A(:,1), the second column of 'C' will consist of B(:,1), the third column of 'C' will consist of elements of A(:,2), the fourth column of 'C' will consist of B(:,2) and so on.

Also, I'd like to know how the same can be applied to cell arrays and how the table of the same format could be constructed from matrices? For loops are ok.

Many thanks.

Best Answer

This should work for numeric, cell and table, although Adam's is likely more efficient for numeric:

>> x1 = array2table(rand(3))
x1 =
  3×3 table
     Var1        Var2       Var3  
    _______    ________    _______
    0.77917     0.56882    0.33712
    0.93401     0.46939    0.16218
    0.12991    0.011902    0.79428
>> x2 = array2table(randn(3),'VariableNames',{'Var4' 'Var5' 'Var6'})
x2 =
  3×3 table
      Var4        Var5        Var6  
    ________    ________    ________
    -0.88803     0.30352     0.73936
     0.10009    -0.60033      1.7119
    -0.54453     0.48997    -0.19412
>> x = [x1 x2]
x =
  3×6 table
     Var1        Var2       Var3        Var4        Var5        Var6  
    _______    ________    _______    ________    ________    ________
    0.77917     0.56882    0.33712    -0.88803     0.30352     0.73936
    0.93401     0.46939    0.16218     0.10009    -0.60033      1.7119
    0.12991    0.011902    0.79428    -0.54453     0.48997    -0.19412
>> x = x(:,[(1:3)+[0;3]]) % requires 16b or later, otherwise use bsxfun
x =
  3×6 table
     Var1        Var4        Var2        Var5       Var3        Var6  
    _______    ________    ________    ________    _______    ________
    0.77917    -0.88803     0.56882     0.30352    0.33712     0.73936
    0.93401     0.10009     0.46939    -0.60033    0.16218      1.7119
    0.12991    -0.54453    0.011902     0.48997    0.79428    -0.19412

Related Solutions

MATLAB: How to combine table arrays including the same variable name horizontally

You can use join function if the values held by the same variable name are the same.

>> T = join(T1,T2);
T =
5×3 table
x1 x2 x3   
    _________    ________    ________
0.10665 0.86869 0.86869
       0.9619 0.084436 0.084436
    0.0046342 0.39978 0.39978
      0.77491 0.25987 0.25987
       0.8173 0.80007 0.80007

If the table retains different values in the same variable, there are possible ways to do this.

Detect the same variable name and change the variable name
Create a common variable that is the key and combine it with innerjoin function

1. Detect the same variable name and change the variable name

T1 = array2table(rand(5,2),'VariableNames',{'x1','x2'});
T2 = array2table(rand(5,2),'VariableNames',{'x1','x3'});
% Detect if there is the same variable name
ind = contains(T2. Properties.VariableNames,T1. Properties.VariableNames);
T2. Properties.VariableNames{ind} = [T2. Properties.VariableNames{ind},'_T2']; % Change variable name
T_all = [T1,T2]; % join
>> T_all
T_all =
5×4 table
x1 x2 x1_T2 x3   
    ________    ________    ________    ________
0.075854 0.12991 0.45054 0.82582
     0.05395 0.56882 0.083821 0.53834
      0.5308 0.46939 0.22898 0.99613
     0.77917 0.011902 0.91334 0.078176
     0.93401 0.33712 0.15238 0.44268

2. Create a common variable that is the key and combine it with innerjoin function

T1 = array2table(rand(5,2),'VariableNames',{'x1','x2'});
T2 = array2table(rand(5,2),'VariableNames',{'x1','x3'});
Add variable that is % Key
T1. Key = (1:height(T1))';
T2. Key = (1:height(T2))';
T_all = innerjoin (T1,T2,'Keys','Key') % Join
T_all. Key = [] % Delete Key 
>> T_all
T_all =
5×4 table
x1_T1         x2       x1_T2         x3   
    ________    ________    ________    ________
0.075854     0.12991     0.45054     0.82582
     0.05395     0.56882    0.083821     0.53834
      0.5308     0.46939     0.22898     0.99613
     0.77917    0.011902     0.91334    0.078176
     0.93401     0.33712     0.15238     0.44268

MATLAB: Table: group by datetime

It isn't possible. To illustrate, I'll sum by matching date (instead of hour) using datetime versus datenum.

VALUE=[2;3;4];
dt = datetime(2015,[1;2;1],1);
tbl_dt=table(dt,VALUE,'VariableNames',{'dt','VALUE'});
tbl_dt=varfun(@nansum,tbl_dt,'GroupingVariables',{'dt'});

MATLAB returns

Error using table/varfun (line 154)
A grouping variable must be a categorical, numeric, or logical vector, a cell vector of strings, or a 2D character array.

Now use datenum instead:

dn = datenum(2015,[1;2;1],1);
tbl_dn=table(dn,VALUE,'VariableNames',{'dn','VALUE'});
tbl_dn=varfun(@nansum,tbl_dn,'GroupingVariables',{'dn'});

Because datenum is an integer, MATLAB has no problem:

tbl_dn = 
                    dn        GroupCount    nansum_VALUE
                __________    __________    ____________
      735965    7.3597e+05    2             6           
      735996      7.36e+05    1             3

If you have table variables with dates or times and need to do grouping or summary functions (i.e. varfun or grpstats), this makes datetime pretty much useless. You could work around it by casting the value from datetime to datenum around each operation. Perhaps there is a forthcoming modification to varfun that would solve this limitation.

Best Answer

Related Solutions

MATLAB: How to combine table arrays including the same variable name horizontally

MATLAB: Table: group by datetime

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