Matrix of scatter plots by group

`gplotmatrix(x,y,group)`

gplotmatrix(x,y,group,* clr*,

`sym`

gplotmatrix(x,y,group,

`clr`

`sym`

`doleg`

gplotmatrix(x,y,group,

`clr`

`sym`

`doleg`

`dispopt`

gplotmatrix(x,y,group,

`clr`

`sym`

`doleg`

`dispopt`

[h,ax,bigax] = gplotmatrix(...)

`gplotmatrix(x,y,group)`

creates
a matrix of scatter plots. Each individual set of axes in the resulting
figure contains a scatter plot of a column of `x`

against
a column of `y`

. All plots are grouped by the grouping
variable `group`

.

`x`

and `y`

are matrices with
the same number of rows. If `x`

has *p* columns
and `y`

has *q* columns, the figure
contains a *p*-by-*q* matrix
of scatter plots. If you omit `y`

or specify it as
the empty matrix, `[]`

, `gplotmatrix`

creates
a square matrix of scatter plots of columns of `x`

against
each other.

`group`

is a grouping variable that can be
a categorical variable, vector, character array, or cell array of
character vectors. `group`

must have the same number
of rows as `x`

and `y`

. Points with
the same value of `group`

are placed in the same
group, and appear on the graph with the same marker and color. Alternatively, `group`

can
be a cell array containing several grouping variables (such as ```
{g1
g2 g3}
```

); in that case, observations are in the same group
if they have common values of all grouping variables.

`gplotmatrix(x,y,group,`

specifies
the color, marker type, and size for each group. * clr*,

`sym`

`clr`

`plot`

function. `sym`

`plot`

command,
with the default value `'.'`

. `siz`

is
a vector of sizes, with the default value determined based on the
number of observations. If you do not specify enough values for all
groups, `gplotmatrix`

cycles through the specified
values as needed.`gplotmatrix(x,y,group,`

controls
whether a legend is displayed on the graph (* clr*,

`sym`

`doleg`

`doleg`

`'on'`

, the default)
or not (`doleg`

`'off'`

).`gplotmatrix(x,y,group,`

controls
what appears along the diagonal of a plot matrix of * clr*,

`sym`

`doleg`

`dispopt`

`y`

versus `x`

.
Allowable values are `'none'`

, to leave the diagonals
blank, `'hist'`

, to plot histograms, `'stairs'`

to
display the outlines of grouped histograms (default if there is more
than one group), `'grpbars'`

to plot grouped histogram
bars. or `'variable'`

, to write the variable names. `gplotmatrix`

displays
histograms along the diagonal only when there is only one variable
(i.e., `gplotmatrix(x,[],[],[],[],[],[],'hist')`

.`gplotmatrix(x,y,group,`

specifies
the names of the columns in the * clr*,

`sym`

`doleg`

`dispopt`

`x`

and `y`

arrays.
These names are used to label the `xnam`

and `ynam`

must
be character arrays or cell arrays of character vectors, with one
name for each column of `x`

and `y`

,
respectively.`[h,ax,bigax] = gplotmatrix(...)`

returns
three arrays of handles. `h`

is an array of handles
to the lines on the graphs. The array's third dimension corresponds
to groups in the input argument `group`

. `ax`

is
a matrix of handles to the axes of the individual plots. If

is `dispopt`

`'hist'`

, `'stairs'`

,
or `'grpbars'`

, `ax`

contains one
extra row of handles to invisible axes in which the histograms are
plotted. `bigax`

is a handle to big (invisible) axes
framing the entire plot matrix. `bigax`

is fixed
to point to the current axes, so a subsequent `title`

, `xlabel`

,
or `ylabel`

command will produce labels that are
centered with respect to the entire plot matrix.

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