Randomly labels two or more spatial point patterns (M.A. Mugglestone, S.A. Harding, B.Y.Y. Lee, P.J. Diggle & B.S. Rowlingson).
Options
PRINT = string token |
What to print (summary); default summ |
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SEED = scalar |
Seed for the random numbers used to create the random labellings; default 0 |
Parameters
OLDY = variates |
Vertical coordinates of two or more spatial point patterns; no default – this parameter must be set |
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OLDX = variates |
Horizontal coordinates of two or more spatial point patterns; no default – this parameter must be set |
NEWY = variates |
Variates to receive the vertical coordinates of the spatial point patterns created by random labelling |
NEWX = variates |
Variates to receive the horizontal coordinates of the spatial point patterns created by random labelling |
Description
This procedure pools the coordinates of two or more spatial point patterns (specified using the OLDX and OLDY parameters) and randomly groups (or labels) the points to form n new patterns, where n is the number of patterns supplied using OLDX and OLDY. Each new pattern contains the same number of points as its old counterpart. The coordinates of the new patterns can be saved using the parameters NEWX and NEWY. The SEED option allows a seed to be supplied for generating the random numbers used to create the random labelling (thereby producing reproducible results). If this is not supplied, the default of 0 initializes the random number generator (if necessary) from the system clock.
Printed output is controlled using the PRINT option. The default setting of summary prints the coordinates of each randomly labelled pattern under the headings NEWX[i] and NEWY[i], (i = 1 … n).
Options: PRINT, SEED.
Parameters: OLDY, OLDX, NEWY, NEWX.
Method
A procedure PTCHECKXY is called to check that each pair of structures in OLDX and OLDY have identical restrictions. The procedure APPEND is then used to create a single variate containing the horizontal coordinates of all the point patterns and a factor whose levels indicate the source (original label) of the points. The vertical coordinates are combined in a similar way. The URAND and SORT functions are then used to randomly permute the labels. Finally, the RESTRICT directive is used to extract the horizontal and vertical coordinates corresponding to each level of the permuted factor.
Action with RESTRICT
If any of the variates in OLDX and OLDY are restricted, only the subset of values specified by the restriction will be included in the calculations.
See also
Procedures: GRCSR, GRTHIN, GRTORSHIFT.
Commands for: Calculations and manipulation, Spatial statistics.
Example
CAPTION 'GRLABEL example'; STYLE=meta
VARIATE xcross; VALUES=!( 4, 5, 6, 6, 6, 6, 7, 8)
& ycross; VALUES=!(16,16,14,15,17,18,16,16)
& xcircle; VALUES=!(14,14,15,15,16,16,17,17)
& ycircle; VALUES=!(10,11, 9,12, 9,12,10,11)
GRLABEL [PRINT=*; SEED=841641] OLDY=ycross,ycircle; OLDX=xcross,xcircle;\
NEWY=rly1,rly2; NEWX=rlx1,rlx2
DPTMAP [YLOWER=0; YUPPER=20; XLOWER=0; XUPPER=20]\
Y=rly1,rly2; X=rlx1,rlx2