# NhlDataToNDC (datatondc)

Converts data units into normalized device coordinates (NDCs).
(See NhlDataToNDC.)
Two names are provided for this NCL procedure: the formal name is
NhlDataToNDC, and the abbreviated name is datatondc.

## Synopsis

procedure NhlDataToNDC(
plot[1] : graphic,
x_in[*] : float,
y_in[*] : float,
x_out[*] : float,
y_out[*] : float
)
or
procedure datatondc(
plot[1] : graphic,
x_in[*] : float,
y_in[*] : float,
x_out[*] : float,
y_out[*] : float
)

## Arguments

*plot*
HLU plot.
*x_in*
Single-dimensioned floating-point vector of x data coordinates.
*y_in*
Single-dimensioned floating-point vector of y data coordinates; must be
the same size as *x_in*.
*x_out*
Single-dimensioned floating-point vector the same size as *x_in*;
will contain x-coordinate output for **datatondc**.
*y_out*
Single-dimensioned floating-point vector the same size as *x_out*;
will contain y-coordinate output from **datatondc**.

## Description

The **NhlDataToNDC** procedure uses the built-in transformation
mapping feature of HLU plot objects to map data coordinates into Normalized
Device Coordinates (screen coordinates). All four floating-point parameters must
have the same number of elements. **NhlDataToNDC** maps coordinate
pairs from *x_in* and *y_in* and places the results in the
corresponding elements of *x_out* and *y_out* respectively.
Both *x_out* and *y_out* can be the same variables as
*x_in* and *y_in*. When the data coordinates are outside of
the data transformation specified in the plot, a missing value is placed in
both of the corresponding indexes in the output arrays. The missing value
chosen is either the *x_in* missing value, *y_in* missing value,
or a system default.

### Reference Manual Control Panel

NG4.1 Home, Index, Examples, Glossary, Feedback, Ref Contents, Ref WhereAmI?

* $Revision: 1.10 $ $Date: 1998/09/17 16:10:44 $ *