help mkmat, help svmat, help matname dialogs: mkmat svmat
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Title
[P] matrix mkmat -- Convert variables to matrix and vice versa
Syntax
Create matrix from variables
mkmat varlist [if] [in] [, matrix(matname) nomissing
rownames(varname) roweq(varname) rowprefix(string) obs
nchar(#)]
Create variables from matrix
svmat [type] A [, names(col|eqcol|matcol|string)]
Rename rows and columns of matrix
matname A namelist [, rows(range) columns(range) explicit]
where A is the name of an existing matrix, type is a storage type for new
variables, and namelist is one of
1) a varlist, i.e., names of existing variables possibly
abbreviated;
2) _cons and the names of existing variables possibly abbreviated;
3) arbitrary names when the explicit option is specified.
To reset problem-size limits, see [R] matsize.
Menu
mkmat
Data > Matrices, ado language > Convert variables to matrix
svmat
Data > Matrices, ado language > Convert matrix to variables
Description
mkmat stores the variables listed in varlist in column vectors of the
same name, that is, N x 1 matrices, where N = _N, the number of
observations in the dataset. Optionally, they can be stored as an N x k
matrix, where k is the number of variables in varlist. The variable
names are used as column names. By default, the rows are named r1, r2,
....
svmat takes a matrix and stores its columns as new variables. It is the
reverse of the mkmat command, which creates a matrix from existing
variables.
matname renames the rows and columns of a matrix. matname differs from
the matrix rownames and matrix colnames commands in that matname expands
varlist abbreviations and allows a restricted range for the rows and
columns. See [P] matrix rownames.
Options
matrix(matname) requests that the vectors be combined in a matrix instead
of creating the column vectors.
nomissing specifies that observations with missing values in any of the
variables be excluded ("listwise deletion").
rownames(varname) and roweq(varname) specify that the row names and row
equations of the created matrix or vectors be taken from varname.
varname should be a string variable or an integer positive-valued
numeric variable. (Value labels are ignored; use decode if you want
to use value labels.) Within the names, spaces and periods are
replaced by an underscore (_).
rowprefix(string) specifies that the string string be prefixed to the row
names of the created matrix or column vectors. In the prefix, spaces
and periods are replaced by an underscore (_). If rownames() is not
specified, rowprefix() defaults to r, and to nothing otherwise.
obs specifies that the observation numbers be used as row names. This
option may not be combined with rownames().
nchar(#) specifies that row names be truncated to # characters, 1<=#<=32.
The default is nchar(32).
names(col|eqcol|matcol|string) specifies how the new variables are to be
named.
names(col) uses the column names of the matrix to name the variables.
names(eqcol) uses the equation names prefixed to the column names.
names(matcol) uses the matrix name prefixed to the column names.
names(string) names the variables string1, string2, ..., stringn,
where string is a user-specified string and n is the number of
columns of the matrix.
If names() is not specified, the variables are named A1, A2, ...,
where A is the name of the matrix.
rows(range) and columns(range) specify the rows and columns of the matrix
to rename. The number of rows or columns specified must be equal to
the number of names in namelist. If both rows() and columns() are
given, the specified rows are named namelist, and the specified
columns are also named namelist. The range must be given in one of
the following forms:
rows(.) renames all the rows
rows(2..8) renames rows 2 through 8
rows(3) renames only row 3
rows(4...) renames row 4 to the last row
If neither rows() nor columns() is given, rows(.) columns(.) is the
default. That is, the matrix must be square, and both the rows and
the columns are named namelist.
explicit suppresses the expansion of varlist abbreviations and omits the
verification that the names are those of existing variables. That
is, the names in namelist are used explicitly and can be any valid
row or column names.
Remarks on mkmat
Although cross-products of variables can be loaded into a matrix with the
matrix accum command, programmers may sometimes find it more convenient
to work with the variables in their datasets as vectors instead of as
cross-products. mkmat allows the user a simple way to load specific
variables into matrices in Stata's memory.
Examples
Setup
. sysuse auto
Store mpg in column vector mpg
. mkmat mpg
List the contents of vector mpg
. matrix list mpg
Create matrix X with columns consisting of the values for foreign,
weight, and displacement
. mkmat foreign weight displacement, matrix(X)
List the contents of matrix X
. matrix list X
Create vector b
. matrix b = invsym(X'*X) * X'*mpg
Run a linear regression
. regress mpg foreign weight displacement, noconstant
Create matrix c containing the transpose of the coefficient vector
. matrix c = e(b)'
List the vectors b and c
. matrix list b
. matrix list c
Create matrix D, where the first column contains vector b
. matrix D = b, c
List the contents of matrix D
. matrix list D
Save the columns of D as variables in the dataset with names reg1 and
reg2
. svmat D, names(reg)
List the result
. list make price reg1 reg2 in 1/5
Create vector f by appending vector c to the end of vector b
. matrix f = b\c
Rename row two of f "wgt", where "wgt" does not currently exist as a
variable
. matname f wgt, rows(2) explicit
List the contents of vector f
. matrix list f
Correspondence analysis of indicator matrix
Setup
. webuse ca_smoking, clear
Create indicator variables S1 and S2 for smoking
. tab smoking, gen(S)
Create indicator variables for rank
. tab rank, gen(R)
Create matrix ISR with columns consisting of the values of the indicator
variables
. mkmat S* R*, matrix(ISR)
List the contents of matrix ISR
. mat list ISR
Perform simple correspondence analysis on ISR
. camat ISR, dim(3)
Also see
Manual: [P] matrix mkmat
Help: [P] matrix, [M-4] stata
