# plvect.3plplot - Man Page

Vector plot

## Synopsis

plvect(u, v, nx, ny, scale, pltr, pltr_data)

## Description

Draws a plot of vector data contained in the matrices (u[nx][ny],v[nx][ny]) . The scaling factor for the vectors is given by scale. A transformation routine pointed to by pltr with a pointer pltr_data for additional data required by the transformation routine to map indices within the matrices to the world coordinates. The style of the vector arrow may be set using plsvect(3plplot).

Redacted form: plvect(u, v, scale, pltr, pltr_data) where (see above discussion) the pltr, pltr_data callback arguments are sometimes replaced by a tr vector with 6 elements, or xg and yg array arguments with either one or two dimensions.

This function is used in example 22.

## Arguments

u, v (PLFLT_MATRIX(3plplot), input)

A pair of matrices containing the x and y components of the vector data to be plotted.

nx, ny (PLINT(3plplot), input)

Dimensions of the matrices u and v.

scale (PLFLT(3plplot), input)

Parameter to control the scaling factor of the vectors for plotting. If scale = 0  then the scaling factor is automatically calculated for the data. If scale < 0 then the scaling factor is automatically calculated for the data and then multiplied by -scale. If scale > 0 then the scaling factor is set to scale.

pltr (PLTRANSFORM_callback(3plplot), input)

A callback function that defines the transformation between the zero-based indices of the matrices u and v and world coordinates.For the C case, transformation functions are provided in the PLplot library: pltr0(3plplot) for the identity mapping, and pltr1(3plplot) and pltr2(3plplot) for arbitrary mappings respectively defined by vectors and matrices.  In addition, C callback routines for the transformation can be supplied by the user such as the mypltr function in examples/c/x09c.c which provides a general linear transformation between index coordinates and world coordinates.For languages other than C you should consult the PLplot documentation for the details concerning how PLTRANSFORM_callback(3plplot) arguments are interfaced. However, in general, a particular pattern of callback-associated arguments such as a tr vector with 6 elements; xg and yg vectors; or xg and yg matrices are respectively interfaced to a linear-transformation routine similar to the above mypltr function; pltr1(3plplot); and pltr2(3plplot). Furthermore, some of our more sophisticated bindings (see, e.g., the PLplot documentation) support native language callbacks for handling index to world-coordinate transformations.  Examples of these various approaches are given in examples/<language>x09*, examples/<language>x16*, examples/<language>x20*, examples/<language>x21*, and examples/<language>x22*, for all our supported languages.

pltr_data (PLPointer(3plplot), input)

Extra parameter to help pass information to pltr0(3plplot), pltr1(3plplot), pltr2(3plplot), or whatever callback routine that is externally supplied.

## Authors

Many developers (who are credited at http://plplot.org/credits.php) have contributed to PLplot over its long history.

## See Also

PLplot documentation at http://plplot.org/documentation.php.

## Info

March, 2021 PLplot API