improved scaling for --logarithmic mode ... -- beat.zahnd space.unibe.ch

git-svn-id: svn://svn.oetiker.ch/rrdtool/branches/1.2@824 a5681a0c-68f1-0310-ab6d-d61299d08faa

diff --git a/program/src/rrd_graph.c b/program/src/rrd_graph.c
index 201ee4c61fc2a31c66b3dc8e4413aa12382d6d95..938132ac442fbb48e720a76d22d3ca97ac5a6b0e 100644 (file)
--- a/program/src/rrd_graph.c
+++ b/program/src/rrd_graph.c
@@ -63,19 +63,6 @@ xlab_t xlab[] = {
     {-1,0,TMT_MONTH,0,TMT_MONTH,0,TMT_MONTH,0,0,""}
 };
 
-/* sensible logarithmic y label intervals ...
-   the first element of each row defines the possible starting points on the
-   y axis ... the other specify the */
-
-double yloglab[][12]= {{ 1e9, 1,  0,  0,  0,   0,  0,  0,  0,  0,  0,  0 },
-                      {  1e3, 1,  0,  0,  0,   0,  0,  0,  0,  0,  0,  0 },
-                      {  1e1, 1,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0 },
-                      /* {  1e1, 1,  5,  0,  0,  0,  0,  0,  0,  0,  0,  0 }, */
-                      {  1e1, 1,  2.5,  5,  7.5,  0,  0,  0,  0,  0,  0,  0 },
-                      {  1e1, 1,  2,  4,  6,  8,  0,  0,  0,  0,  0,  0 },
-                      {  1e1, 1,  2,  3,  4,  5,  6,  7,  8,  9,  0,  0 },
-                      {  0,   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0 }};
-
 /* sensible y label intervals ...*/
 
 ylab_t ylab[]= {
@@ -1096,20 +1083,30 @@ data_proc( image_desc_t *im ){
        there was no data in the graph ... this is not good ...
        lets set these to dummy values then ... */
 
-    if (isnan(minval)) minval = 0.0;
-    if (isnan(maxval)) maxval = 1.0;
+    if (im->logarithmic) {
+       if (isnan(minval)) minval = 0.2;
+       if (isnan(maxval)) maxval = 5.1;
+    }
+    else {
+       if (isnan(minval)) minval = 0.0;
+       if (isnan(maxval)) maxval = 1.0;
+    }
     
     /* adjust min and max values */
     if (isnan(im->minval) 
-       /* don't adjust low-end with log scale */
-       || ((!im->logarithmic && !im->rigid) && im->minval > minval)
-       )
-       im->minval = minval;
+       /* don't adjust low-end with log scale */ /* why not? */
+       || ((!im->rigid) && im->minval > minval)
+       ) {
+       if (im->logarithmic)
+           im->minval = minval * 0.5;
+       else
+           im->minval = minval;
+    }
     if (isnan(im->maxval) 
        || (!im->rigid && im->maxval < maxval)
        ) {
        if (im->logarithmic)
-           im->maxval = maxval * 1.1;
+           im->maxval = maxval * 2.0;
        else
            im->maxval = maxval;
     }
@@ -1691,100 +1688,225 @@ int draw_horizontal_grid(image_desc_t *im)
     return 1;
 }
 
+/* this is frexp for base 10 */
+double frexp10(double, double *);
+double frexp10(double x, double *e) {
+    double mnt;
+    int iexp;
+
+    iexp = floor(log(fabs(x)) / log(10));
+    mnt = x / pow(10.0, iexp);
+    if(mnt >= 10.0) {
+       iexp++;
+       mnt = x / pow(10.0, iexp);
+    }
+    *e = iexp;
+    return mnt;
+}
+
 /* logaritmic horizontal grid */
 int
 horizontal_log_grid(image_desc_t   *im)   
 {
-    double   pixpex;
-    int      ii,i;
-    int      minoridx=0, majoridx=0;
-    char     graph_label[100];
-    double   X0,X1,Y0;   
-    double   value, pixperstep, minstep;
+    double yloglab[][10] = {
+       {1.0, 10., 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0},
+       {1.0, 5.0, 10., 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0},
+       {1.0, 2.0, 5.0, 7.0, 10., 0.0, 0.0, 0.0, 0.0, 0.0},
+       {1.0, 2.0, 4.0, 6.0, 8.0, 10., 0.0, 0.0, 0.0, 0.0},
+       {1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.}};
+
+    int i, j, val_exp, min_exp;
+    double nex;                /* number of decades in data */
+    double logscale;   /* scale in logarithmic space */
+    int exfrac = 1;    /* decade spacing */
+    int mid = -1;      /* row in yloglab for major grid */
+    double mspac;      /* smallest major grid spacing (pixels) */
+    int flab;          /* first value in yloglab to use */
+    double value, tmp;
+    double X0,X1,Y0;   
+    char graph_label[100];
 
-    /* find grid spaceing */
-    pixpex= (double)im->ysize / (log10(im->maxval) - log10(im->minval));
+    nex = log10(im->maxval / im->minval);
+    logscale = im->ysize / nex;
 
-       if (isnan(pixpex)) {
-               return 0;
-       }
+    /* major spacing for data with high dynamic range */
+    while(logscale * exfrac < 3 * im->text_prop[TEXT_PROP_LEGEND].size) {
+       if(exfrac == 1) exfrac = 3;
+       else exfrac += 3;
+    }
 
-    for(i=0;yloglab[i][0] > 0;i++){
-       minstep = log10(yloglab[i][0]);
-       for(ii=1;yloglab[i][ii+1] > 0;ii++){
-           if(yloglab[i][ii+2]==0){
-               minstep = log10(yloglab[i][ii+1])-log10(yloglab[i][ii]);
-               break;
+    /* major spacing for less dynamic data */
+    do {
+       /* search best row in yloglab */
+       mid++;
+       for(i = 0; yloglab[mid][i + 1] < 10.0; i++);
+       mspac = logscale * log10(10.0 / yloglab[mid][i]);
+    } while(mspac > 2 * im->text_prop[TEXT_PROP_LEGEND].size && mid < 5);
+    if(mid) mid--;
+
+    /* find first value in yloglab */
+    for(flab = 0; frexp10(im->minval, &tmp) > yloglab[mid][flab]; flab++);
+    if(yloglab[mid][flab] == 10.0) {
+       tmp += 1.0;
+       flab = 0;
+    }
+    val_exp = tmp;
+    if(val_exp % exfrac) val_exp += abs(-val_exp % exfrac);
+
+    X0=im->xorigin;
+    X1=im->xorigin+im->xsize;
+
+    /* draw grid */
+    while(1) {
+       value = yloglab[mid][flab] * pow(10.0, val_exp);
+
+       Y0 = ytr(im, value);
+       if(Y0 <= im->yorigin - im->ysize) break;
+
+       /* major grid line */
+       gfx_new_dashed_line ( im->canvas,
+           X0-2,Y0,
+           X1+2,Y0,
+           MGRIDWIDTH, im->graph_col[GRC_MGRID],
+           im->grid_dash_on, im->grid_dash_off);
+
+       /* label */
+       if (im->extra_flags & FORCE_UNITS_SI) {
+           int scale;
+           double pvalue;
+           char symbol;
+
+           scale = floor(val_exp / 3.0);
+           if( value >= 1.0 ) pvalue = pow(10.0, val_exp % 3);
+           else pvalue = pow(10.0, ((val_exp + 1) % 3) + 2);
+           pvalue *= yloglab[mid][flab];
+
+           if ( ((scale+si_symbcenter) < (int)sizeof(si_symbol)) &&
+               ((scale+si_symbcenter) >= 0) )
+               symbol = si_symbol[scale+si_symbcenter];
+           else
+               symbol = '?';
+
+               sprintf(graph_label,"%3.0f %c", pvalue, symbol);
+        } else
+           sprintf(graph_label,"%3.0e", value);
+       gfx_new_text ( im->canvas,
+           X0-im->text_prop[TEXT_PROP_AXIS].size, Y0,
+           im->graph_col[GRC_FONT],
+           im->text_prop[TEXT_PROP_AXIS].font,
+           im->text_prop[TEXT_PROP_AXIS].size,
+           im->tabwidth,0.0, GFX_H_RIGHT, GFX_V_CENTER,
+           graph_label );
+
+       /* minor grid */
+       if(mid < 4 && exfrac == 1) {
+           /* find first and last minor line behind current major line
+            * i is the first line and j tha last */
+           if(flab == 0) {
+               min_exp = val_exp - 1;
+               for(i = 1; yloglab[mid][i] < 10.0; i++);
+               i = yloglab[mid][i - 1] + 1;
+               j = 10;
+           }
+           else {
+               min_exp = val_exp;
+               i = yloglab[mid][flab - 1] + 1;
+               j = yloglab[mid][flab];
+           }
+
+           /* draw minor lines below current major line */
+           for(; i < j; i++) {
+
+               value = i * pow(10.0, min_exp);
+               if(value < im->minval) continue;
+
+               Y0 = ytr(im, value);
+               if(Y0 <= im->yorigin - im->ysize) break;
+
+               /* draw lines */
+               gfx_new_dashed_line ( im->canvas,
+                   X0-1,Y0,
+                   X1+1,Y0,
+                   GRIDWIDTH, im->graph_col[GRC_GRID],
+                   im->grid_dash_on, im->grid_dash_off);
            }
        }
-       pixperstep = pixpex * minstep;
-       if(pixperstep > 5){minoridx = i;}
-       if(pixperstep > 2 *  im->text_prop[TEXT_PROP_LEGEND].size){majoridx = i;}
+       else if(exfrac > 1) {
+           for(i = val_exp - exfrac / 3 * 2; i < val_exp; i += exfrac / 3) {
+               value = pow(10.0, i);
+               if(value < im->minval) continue;
+
+               Y0 = ytr(im, value);
+               if(Y0 <= im->yorigin - im->ysize) break;
+
+               /* draw lines */
+               gfx_new_dashed_line ( im->canvas,
+                   X0-1,Y0,
+                   X1+1,Y0,
+                   GRIDWIDTH, im->graph_col[GRC_GRID],
+                   im->grid_dash_on, im->grid_dash_off);
+           }
+       }
+
+       /* next decade */
+       if(yloglab[mid][++flab] == 10.0) {
+           flab = 0;
+           val_exp += exfrac;
+       }
     }
-   
-   X0=im->xorigin;
-   X1=im->xorigin+im->xsize;
-    /* paint minor grid */
-    for (value = pow((double)10, log10(im->minval) 
-                         - fmod(log10(im->minval),log10(yloglab[minoridx][0])));
-        value  <= im->maxval;
-        value *= yloglab[minoridx][0]){
-       if (value < im->minval) continue;
-       i=0;    
-       while(yloglab[minoridx][++i] > 0){          
-          Y0 = ytr(im,value * yloglab[minoridx][i]);
-          if (Y0 <= im->yorigin - im->ysize) break;
-          gfx_new_dashed_line ( im->canvas,
-                         X0-1,Y0,
-                         X1+1,Y0,
-                         GRIDWIDTH, im->graph_col[GRC_GRID],
-                         im->grid_dash_on, im->grid_dash_off);
+
+    /* draw minor lines after highest major line */
+    if(mid < 4 && exfrac == 1) {
+       /* find first and last minor line below current major line
+        * i is the first line and j tha last */
+       if(flab == 0) {
+           min_exp = val_exp - 1;
+           for(i = 1; yloglab[mid][i] < 10.0; i++);
+           i = yloglab[mid][i - 1] + 1;
+           j = 10;
+       }
+       else {
+           min_exp = val_exp;
+           i = yloglab[mid][flab - 1] + 1;
+           j = yloglab[mid][flab];
+       }
+
+       /* draw minor lines below current major line */
+       for(; i < j; i++) {
+
+           value = i * pow(10.0, min_exp);
+           if(value < im->minval) continue;
+
+           Y0 = ytr(im, value);
+           if(Y0 <= im->yorigin - im->ysize) break;
+
+           /* draw lines */
+           gfx_new_dashed_line ( im->canvas,
+               X0-1,Y0,
+               X1+1,Y0,
+               GRIDWIDTH, im->graph_col[GRC_GRID],
+               im->grid_dash_on, im->grid_dash_off);
+       }
+    }
+    /* fancy minor gridlines */
+    else if(exfrac > 1) {
+       for(i = val_exp - exfrac / 3 * 2; i < val_exp; i += exfrac / 3) {
+           value = pow(10.0, i);
+           if(value < im->minval) continue;
+
+           Y0 = ytr(im, value);
+           if(Y0 <= im->yorigin - im->ysize) break;
+
+           /* draw lines */
+           gfx_new_dashed_line ( im->canvas,
+               X0-1,Y0,
+               X1+1,Y0,
+               GRIDWIDTH, im->graph_col[GRC_GRID],
+               im->grid_dash_on, im->grid_dash_off);
        }
     }
 
-    /* paint major grid and labels*/
-    for (value = pow((double)10, log10(im->minval) 
-                         - fmod(log10(im->minval),log10(yloglab[majoridx][0])));
-        value <= im->maxval;
-        value *= yloglab[majoridx][0]){
-       if (value < im->minval) continue;
-       i=0;    
-       while(yloglab[majoridx][++i] > 0){          
-          Y0 = ytr(im,value * yloglab[majoridx][i]);    
-          if (Y0 <= im->yorigin - im->ysize) break;
-          gfx_new_dashed_line ( im->canvas,
-                         X0-2,Y0,
-                         X1+2,Y0,
-                         MGRIDWIDTH, im->graph_col[GRC_MGRID],
-                         im->grid_dash_on, im->grid_dash_off);
-
-          if (im->extra_flags & FORCE_UNITS_SI) {
-             double pvalue = value * yloglab[majoridx][i];
-             double scale = floor( log10( fabs(pvalue)) / 3);
-             char symbol;
-
-             pvalue /= pow(10, 3*scale);
-
-             if ( ((scale+si_symbcenter) < sizeof(si_symbol)) &&
-                  ((scale+si_symbcenter) >= 0) )
-                symbol = si_symbol[(int)scale+si_symbcenter];
-             else
-                symbol = '?';
-
-             sprintf(graph_label,"%3.0f %c", pvalue, symbol);
-          } else
-             sprintf(graph_label,"%3.0e",value * yloglab[majoridx][i]);
-
-          gfx_new_text ( im->canvas,
-                         X0-im->text_prop[TEXT_PROP_AXIS].size, Y0,
-                         im->graph_col[GRC_FONT],
-                         im->text_prop[TEXT_PROP_AXIS].font,
-                         im->text_prop[TEXT_PROP_AXIS].size,
-                         im->tabwidth,0.0, GFX_H_RIGHT, GFX_V_CENTER,
-                         graph_label );
-       } 
-    }
-       return 1;
+    return 1;
 }
 
 
@@ -3266,8 +3388,6 @@ rrd_graph_options(int argc, char *argv[],image_desc_t *im)
 
        case 'o':
            im->logarithmic = 1;
-           if (isnan(im->minval))
-               im->minval=1;
            break;
         case 'c':
             if(sscanf(optarg,
@@ -3390,7 +3510,7 @@ rrd_graph_options(int argc, char *argv[],image_desc_t *im)
        return;
     }
 
-    if (im->logarithmic == 1 && (im->minval <= 0 || isnan(im->minval))){
+    if (im->logarithmic == 1 && im->minval <= 0){
        rrd_set_error("for a logarithmic yaxis you must specify a lower-limit > 0");    
        return;
     }