---
name: "plvect"
section: "3plplot"
platform: "linux"
package: "plplot-doc"
version: "5.15.0+dfsg2-15"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/plvect"
---

# plvect(3plplot)

Vector plot

## NAME

**plvect** - 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)](/plsvect/3plplot.md).

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.