improved ticks and tacks for small log ranges

pub/plot/axis.cpp

@@ -309,20 +309,31 @@ double CAxis::pc(double v) const { return 10 * value2plotcoord(v); }
 double CAxis::pcerr(double v, double dv) const { return 10 * value2ploterror(v, dv); }
 
 
-//! Sets Tacks, *ntpt, *ticklim to a nice division of the plot range.
+//! Sets Tacks, ntpt, nt4t, *ticklim to a nice division of the plot range.
 
-void CAxis::calc_ticks(vector<double>& Tacks, int& ntpt, double* ticklim) const
+void CAxis::calc_ticks(vector<double>& Tacks, int& ntpt, int& nt4t, double* ticklim) const
 {
     if (logflag)
-        calc_logticks(Tacks, ntpt, ticklim);
+        calc_logticks(Tacks, ntpt, nt4t, ticklim);
     else
-        calc_linticks(Tacks, ntpt, ticklim);
+        calc_linticks(Tacks, ntpt, nt4t, ticklim);
 }
 
 
-//! Sets Tacks, *ntpt, *ticklim to a nice division of the plot range.
+//! Sets Tacks, ntpt, nt4t, *ticklim to a nice division of the plot range.
 
-void CAxis::calc_linticks(vector<double>& Tacks, int& ntpt, double* ticklim) const
+void CAxis::calc_linticks(vector<double>& Tacks, int& ntpt, int& nt4t, double* ticklim) const
+{
+    double dtack;
+    calc_lintacks(Tacks, ntpt, dtack);
+    ticklim[0] = Tacks.front() - dtack;
+    ticklim[1] = Tacks.back() + dtack;
+    nt4t = Tacks.size() + 2;
+}
+
+//! Sets Tacks, *ntpt, and dtack
+
+void CAxis::calc_lintacks(vector<double>& Tacks, int& ntpt, double& dtack) const
 {
     if (inf >= sup)
         throw "BUG detected by calc_linticks: inf=" + S(inf) + " >= sup=" + S(sup);
@@ -330,7 +341,6 @@ void CAxis::calc_linticks(vector<double>& Tacks, int& ntpt, double* ticklim) con
     int ir = (int)((r < 0) ? r - 1 : r);
     double rd = r - ir; // fractional part of r
     double rdr = pow(10., rd);
-    double dtack;
     if (rdr > 9.99999) {
         dtack = 2.5 * pow(10., ir); // spacing between tacks
         ntpt = 5; // ticks per tack
@@ -356,14 +366,12 @@ void CAxis::calc_linticks(vector<double>& Tacks, int& ntpt, double* ticklim) con
     for (double d = dtack * (floor(inf/dtack)-1); d < dtack * (ceil(sup/dtack)+1); d += dtack)
         if (vsub <= d && d <= vsup)
             Tacks.push_back(d);
-    ticklim[0] = Tacks.front() - dtack;
-    ticklim[1] = Tacks.back() + dtack;
 }
 
 
-//! Sets Tacks, *ntpt, *ticklim to a nice division of the plot range.
+//! Sets Tacks, ntpt, nt4t, *ticklim to a nice division of the plot range.
 
-void CAxis::calc_logticks(vector<double>& Tacks, int& ntpt, double* ticklim) const
+void CAxis::calc_logticks(vector<double>& Tacks, int& ntpt, int& nt4t, double* ticklim) const
 {
     if (inf >= sup)
         throw "BUG detected by calc_logticks: inf=" + S(inf) + " >= sup=" + S(sup);
@@ -404,6 +412,7 @@ void CAxis::calc_logticks(vector<double>& Tacks, int& ntpt, double* ticklim) con
         if (d1 <= r0 && r0 <= d2)
             Tacks.push_back(r0);
     }
+    nt4t = Tacks.size() + 2;
 
     // set tick limits (may exceed actual tick range)
     int ntack = Tacks.size();
@@ -426,4 +435,11 @@ void CAxis::calc_logticks(vector<double>& Tacks, int& ntpt, double* ticklim) con
     } else {
         ntpt = -incr; // this one has special semantics: it means 'incr' ticks per tack
     }
+
+    // for narrow ranges, overwrite tacks
+    if (ntack<2) {
+        double dtack;
+        int ntpt_dummy;
+        calc_lintacks(Tacks, ntpt_dummy, dtack);
+    }
 }

pub/plot/axis.hpp

@@ -43,7 +43,9 @@ public:
     void set_xgrid(std::vector<double>& x, int n) const;
     double pc(double v) const;
     double pcerr(double v, double dv) const;
-    void calc_ticks(std::vector<double>& Tacks, int& ntpt, double* ticklim) const;
-    void calc_linticks(std::vector<double>& Tacks, int& ntpt, double* ticklim) const;
-    void calc_logticks(std::vector<double>& Tacks, int& ntpt, double* ticklim) const;
+    void calc_ticks(std::vector<double>& Tacks, int& ntpt, int& nt4t, double* ticklim) const;
+private:
+    void calc_linticks(std::vector<double>& Tacks, int& ntpt, int& nt4t, double* ticklim) const;
+    void calc_lintacks(std::vector<double>& Tacks, int& ntpt, double& dtack) const;
+    void calc_logticks(std::vector<double>& Tacks, int& ntpt, int& nt4t, double* ticklim) const;
 };

pub/plot/ps_plotter.cpp

@@ -158,9 +158,10 @@ namespace {
     string ps_ticktack(const CAxis* A)
     {
         vector<double> Tacks;
-        int ntpt;
+        int ticks_per_tack;
+        int ntacks4ticks;
         double ticklim[2];
-        A->calc_ticks(Tacks, ntpt, ticklim);
+        A->calc_ticks(Tacks, ticks_per_tack, ntacks4ticks, ticklim);
 
         string ret;
         int ntack = Tacks.size();
@@ -187,8 +188,8 @@ namespace {
                    % A->name
                    % (float)ticklim[1]
                    % A->name
-                   % (ntack + 2)
-                   % ntpt
+                   % ntacks4ticks
+                   % ticks_per_tack
                    % (A->logflag ? "Log" : "Lin"));
         return ret;
     }