SHUFFLE GROUPS

SHUFFLE GROUPS (LET)

Let Subcommand

Given a response variable and a group-id variable, re-arrange the groups based on an index variable (the response variable is not randomized within the group).

The motivation for this command is to allow the rows (or columns) of a matrix or image to be randomly re-arranged. The randomization can be either with replacement or without replacement (this is determined by the index variable).

The size of the index variable should be equal to the number of groups in the group-id variable. Although this command was motivated by cases where the group sizes are equal, this is not required. If the group sizes are note equal, the output variable may not be the same length as the input variable.

LET <y2> = SHUFFLE GROUPS <y> <x> <index>
                        <SUBSET/EXCEPT/FOR qualification>
where <y> is a response variable;
            <x> is a group-id variable;
            <index> is a variable defining the order for the groups in the output variable;
            <y2> is a response variable containing the re-arranged groups;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.

The response variable and group-id variable should have the same number of elements. The index variable must be the same size as the number of groups in the group-id variable.

If there are k groups in the group-id variable, then the values in the index variable should be between 1 and k. An error will be reported if they are not.

LET Y2 = SHUFFLE GROUPS Y X XINDEX

None

None

RANDOM PERMUTATION	=	Generate a set of random permutations.
MATRIX RENUMBER	=	Permute the rows and columns of a matrix.

Data Manipulation

2014/07

 
. Step 1:   Read the data
.
read x y
1   1
1   2
1   3
1   4
1   5
2  11
2  12
2  13
2  14
2  15
3  21
3  22
3  23
3  24
3  25
4  31
4  32
4  33
4  34
4  35
end of data
.
. Step 2:   Now reshuffle the groups
.
let iindex = data 3  1 4  2
let yout = shuffle groups y x iindex
.
. Step 3:   Print the results
.
set write decimals 0
print x y yout
    

The following output is generated

 
 ---------------------------------------------
               X              Y           YOUT
 ---------------------------------------------
               1              1             21
               1              2             22
               1              3             23
               1              4             24
               1              5             25
               2             11              1
               2             12              2
               2             13              3
               2             14              4
               2             15              5
               3             21             31
               3             22             32
               3             23             33
               3             24             34
               3             25             35
               4             31             11
               4             32             12
               4             33             13
               4             34             14
               4             35             15