---
name: "QwtScaleTransformation"
section: "3"
platform: "linux"
package: "libqwt5-doc"
version: "5.2.3-1"
release: "Debian 10 (Buster)"
platforms: ["linux"]
url: "https://new.carta.tech/QwtScaleTransformation"
---

# QwtScaleTransformation(3)

## NAME

QwtScaleTransformation -

## SYNOPSIS

`#include <qwt_scale_map.h>`

### Public Types

enum **Type** { **Linear**, **Log10**, **Other** }\

### Public Member Functions

**QwtScaleTransformation** (Type **type**)\
 virtual **~QwtScaleTransformation** ()\
 virtual **QwtScaleTransformation** \* **copy** () const \
 virtual double **invXForm** (double x, double p1, double p2, double s1, double s2) const \
 Type **type** () const \
 virtual double **xForm** (double x, double s1, double s2, double p1, double p2) const \

## Detailed Description

Operations for linear or logarithmic (base 10) transformations.

## Member Function Documentation

### double QwtScaleTransformation::invXForm (doublep, doublep1, doublep2, doubles1, doubles2) const` [virtual]`

Transform a value from the coordinate system of the paint device into the coordinate system of a scale. **Parameters:**

*p* Value related to the coordinate system of the paint device \
 *p1* First border of the coordinate system of the paint device \
 *p2* Second border of the coordinate system of the paint device \
 *s1* First border of the coordinate system of the scale \
 *s2* Second border of the coordinate system of the scale

**Returns:**

- **linear mapping:**

  s1 + ( s2 - s1 ) / ( p2 - p1 ) \* ( p - p1 );

- **log10 mapping:**

  exp((p - p1) / (p2 - p1) \* log(s2 / s1)) \* s1;

### QwtScaleTransformation::Type QwtScaleTransformation::type () const` [inline]`

**Returns:**

Transformation type

### double QwtScaleTransformation::xForm (doubles, doubles1, doubles2, doublep1, doublep2) const` [virtual]`

Transform a value from the coordinate system of a scale into the coordinate system of the paint device. **Parameters:**

*s* Value related to the coordinate system of the scale \
 *s1* First border of the coordinate system of the scale \
 *s2* Second border of the coordinate system of the scale \
 *p1* First border of the coordinate system of the paint device \
 *p2* Second border of the coordinate system of the paint device

**Returns:**

- **linear mapping:**

  p1 + (p2 - p1) / (s2 - s1) \* (s - s1);

- **log10 mapping:**

  p1 + (p2 - p1) / log(s2 / s1) \* log(s / s1);

## Author

Generated automatically by Doxygen for Qwt User's Guide from the source code.