[g,gN] = grp2idx(s)
creates an index vector g from the grouping variable
s. The output g is a vector of integer
values from 1 up to the number K of distinct groups.
gN is a cell array of character vectors representing the
list of group names.
[g,gN,gL] = grp2idx(s)
also returns a column vector gL representing the list of the
group levels with the same data type as s.
Create a categorical vector by using discretize and convert it to an index vector by using grp2idx.
Load the hospital data set and convert the ages in hospital.Ages to categorical values representing the ages by decade.
load hospital
edges = 0:10:100; % Bin edges
labels = strcat(num2str((0:10:90)','%d'),{'s'}); % Labels for the bins
s = discretize(hospital.Age,edges,'Categorical',labels);
Display the ages and the groups of ages for the first five samples.
ages = hospital.Age(1:5)
ages = 5×1
38
43
38
40
49
groups = s(1:5)
groups = 5×1 categorical
30s
40s
30s
40s
40s
Create an index vector from the categorical vector s.
[g,gN,gL] = grp2idx(s);
Display the index values corresponding to the first five samples.
g(1:5)
ans = 5×1
4
5
4
5
5
Reproduce the input argument s using the output gL.
gL(g(1:5))
ans = 5×1 categorical
30s
40s
30s
40s
40s
Use gN(g) to reproduce the input argument s as a cell array of character vectors.
gN(g(1:5))
ans = 5×1 cell
{'30s'}
{'40s'}
{'30s'}
{'40s'}
{'40s'}
Grouping variable, specified as a categorical, numeric, logical,
datetime, or duration vector, a string array, a cell
array of character vectors, or a character array with each row representing
a group label.
grp2idx treats NaNs (numeric,
duration, or logical), '' (empty character arrays or cell
arrays of character vectors), "" (empty strings),
<missing> values (string),
<undefined> values (categorical), and
NaTs (datetime) in
s as missing values and returns
NaNs in the corresponding rows of
g. The outputs gN and
gL do not include entries for missing
values.
Group index, returned as a positive integer vector with values from 1 up
to the number K of distinct groups in
s.
List of group names, returned as a cell array of character vectors.
The order of gN depends on the data type of the
grouping variable s.
For numeric and logical vectors, the order is the sorted order of
s.
For categorical vectors, the order is the order of
categories(s).
For other data types, the order is the order of first appearance
in s.
gN(g) reproduces the contents of s
in a cell array.
List of group levels, returned as the same data type as
s: a categorical, numeric, logical,
datetime, or duration vector, a cell array of
character vectors, or a character array with each row representing a group
label. (The software treats string arrays as cell arrays of character
vectors.)
The set of groups and their order in gL are the same
as those in gN, but gL has the
same data type as s.
If s is a character matrix, then
gL(g,:) reproduces s; otherwise,
gL(g) reproduces s.
The input argument s can be a numeric, logical,
or character vector or a cell array of character vectors. Code
generation does not support a categorical, datetime,
or duration vector or a string array for the input argument.
In the generated code, the second and third outputs,
gN and gL, are identical.
gN and gL have the same
data type as the input argument s.
