Re #11422 Implement functions for scaling transformations

Code/Mantid/MantidQt/API/inc/MantidQtAPI/MantidQwtScaleTransformation.h

@@ -28,9 +28,9 @@
 #include "qwt_math.h"
 #include "qwt_scale_map.h"
 
-/*!
-   \brief Operations for power (X^n) transformations
-*/
+/*
+ *  Operations for power (X^n) transformations
+ */
 class QWT_EXPORT MantidQwtScaleTransformation: public QwtScaleTransformation
 {
 public:
@@ -43,6 +43,15 @@ class QWT_EXPORT MantidQwtScaleTransformation: public QwtScaleTransformation
         Other
     };
 
+private:
+    // TODO this should be user input from GUI
+    int nth_power = 2;
+
+    MantidQwtScaleTransformation();
+    MantidQwtScaleTransformation &operator=( const MantidQwtScaleTransformation);
+
+    const Type d_type;
+
 };
 
 #endif

Code/Mantid/MantidQt/API/src/MantidQwtPowerScaleEngine.cpp

@@ -23,7 +23,7 @@ MantidQwtScaleTransformation *MantidQwtPowerScaleEngine::transformation() const
 void MantidQwtPowerScaleEngine::autoScale(int maxNumSteps, 
     double &x1, double &x2, double &stepSize) const
 {
-    const double one_over_n = 1.0/nth_power
+    const double one_over_n = 1.0/nth_power;
 
     if ( x1 > x2 )
         qSwap(x1, x2);

Code/Mantid/MantidQt/API/src/MantidQwtScaleTransformation.cpp

@@ -0,0 +1,35 @@
+#include "MantidQwtScaleTransformation.h"
+
+double MantidQwtScaleTransformation::xForm(
+    double s, double s1, double s2, double p1, double p2) const
+{
+    if (d_type == Log10)  
+        return p1 + (p2 - p1) / log(s2 / s1) * log(s / s1);
+    else if (d_type == Power)
+        return p1 + (p2 - p1) / pow(s2, nth_power) - pow(s1, nth_power)) * (pow(s, nth_power) - pow(s1, nth_power));
+    else 
+        return p1 + (p2 - p1) / (s2 - s1) * (s - s1);
+}
+
+/*
+  Transform a value from a linear to a logarithmic interval
+
+  @param p value related to the linear interval [p1, p2]
+  @param p1 first border of linear interval
+  @param p2 second border of linear interval
+  @param s1 first border of logarithmic interval
+  @param s2 second border of logarithmic interval
+  @return logarithmic or power interval
+*/
+double QwtScaleTransformation::invXForm(double p, double p1, double p2, 
+    double s1, double s2) const
+{
+    if (d_type == Log10)  
+        return exp((p - p1) / (p2 - p1) * log(s2 / s1)) * s1;
+    else if (d_type == Power){
+        const double one_over_n = 1.0/nth_power;
+        return pow((p - p1) / (p2 - p1) * pow(s2, nth_power) - pow(s1, nth_power)), one_over_n) * s1;
+    }
+    else
+        return s1 + (s2 - s1) / (p2 - p1) * (p - p1);
+}