# DGroup

DGroup gnum def The define group command, DGroup, allows programmers and/or users to define new plot groups. The PLT default is for each plot group to consist of a data vector (the SKip command provides another way to override this default). The DGroup command gives the user total control over how the plot groups are defined.

The gnum is the group number and must be in the range 1 to MXGRP-MXMOD (typically 60).

def is the group definition and can be either

a) A single number. The number corresponds to a vector number in the main data array. Thus "DGroup 2 2" would define group 2 to be the second vector, which is the default.

b) Four numbers. If you think of the main data array to be a two dimensional array with coordinates corresponding to the row and vector numbers, then the first two numbers define a row, vector coordinate of one corner and the second set form the other corner. Thus "DGroup 4 5 3 10 3" would define group 4 to be rows 5 through 10 of vector 3, and "DGroup 4 1 1 10 20" would cause group 4 to include rows 1 through 10 and vectors 1 to 20.

c) Either the word Model or Residual. By default, PLT reserves the high numbered groups (typically 61 to 64) to contain the model. However if you want to plot the same model in different window than the default you can define a new group to be that model The "DGroup 3 Res" command would cause group 3 to contain the current model residuals. The data min and max values are recomputed every time the model is changed. Of course, PLT does not change the scale unless you issue a "Rescale" command.

## residual_example

```PLT> MO 1 CO               ! Define a COnstant model
23                        ! Starting parameter
PLT> DGroup 2 Res          ! Group 2 is the model residuals
PLT> YPL 2                 ! Plot group 2 in current window
PLT> R Y                   ! Rescale and replot
PLT> FIT                   ! Fit
PLT> P                     ! Replot using the original scale
PLT> R Y                   ! Rescale using currng residual min/max values
examples
PLT> DGroup 2 2            ! Group 2 is vector 2 (the PLT default)
PLT> DGroup 2 1 2 10 2     ! Group 2 is rows 1 to 10 of vector 2
PLT> DGroup 2 2 1 10 99    ! Group 2 is now two dimensional, consisting
! of rows 2 through 10 and vectors 1 to 99.
PLT> Dgroup 2 Res          ! Group 2 is now the model residuals.
```