Type: Command
Description: PCONTOUR Plot Type Command: Sets the plot type to PCONTOUR.
When plot type is set PCONTOUR, the DRAW command plots a
VPAR is made up of the following elements:
{xleft xright ynear yfar zlow zhigh xmin xmax ymin ymax xeye yeye zeye xstep ystep }
For plot type PCONTOUR, the elements of VPAR are used as follows:
•xleft and xright are real numbers that specify the width of the view space.
•ynear and yfar are real numbers that specify the depth of the view space.
•zlow and zhigh are real numbers that specify the height of the view space.
•xmin and xmax are not used.
•ymin and ymax are not used.
•xeye, yeye, and zeye are real numbers that specify the point in space from which the graph is viewed.
•xstep and ystep are real numbers that set the number of
The plotting parameters are specified in the reserved variable PPAR, which has this form:
{(xmin, ymin) (xmax, ymax) indep res axes ptype depend }
For plot type PCONTOUR, the elements of PPAR are used as follows:
•(xmin, ymin) and (xmax, ymax) are not used.
•indep is a name specifying the independent variable. The default value of indep is X.
•res is not used.
•axes is not used.
•ptype is a command name specifying the plot type. Executing the command PCONTOUR places the name PCONTOUR in ptype.
•depend is a name specifying the dependent variable. The default value is Y.
Access: …µPCONTOUR
Input/Output: None
See also: BAR, CONIC, DIFFEQ, FUNCTION, GRIDMAP, HISTOGRAM, PARAMETRIC, PARSURFACE, POLAR, SCATTER, SLOPEFIELD, TRUTH, WIREFRAME, YSLICE
PCOVType: Command
Description: Population Covariance Command: Returns the population covariance of the independent and dependent data columns in the current statistics matrix (reserved variable ΣDAT).
The columns are specified by the first two elements in reserved variable ΣPAR, set by XCOL and YCOL respectively. If ΣPAR does not exist, PCOV creates it and sets the elements to their default values (1 and 2).
The population covariance is calculated with the following formula:
1 | n |
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∑ (xkn1 – xn1)(xkn2 – xn2) | ||||||
nk = | 1 |
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where xkn1 is the kth coordinate value in column n1 , xkn2 is the kth coordinate value in the
column n2 , xn1 is the mean of the data in column n1 , xn2 is the mean of the data in column n2 , and n is the number of data points.