first try for symlog.ticks

d3#162
Fil · Apr 8, 2019 · aea855f · aea855f
1 parent 8ef7906
commit aea855f
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Showing 4 changed files with 96 additions and 12 deletions.
diff --git a/src/log.js b/src/log.js
@@ -139,7 +139,5 @@ export default function log() {
     return copy(scale, log()).base(scale.base());
   };
 
-  initRange.apply(scale, arguments);
-
-  return scale;
+  return initRange.apply(scale, arguments);
 }
diff --git a/src/ordinal.js b/src/ordinal.js
@@ -40,7 +40,5 @@ export default function ordinal() {
     return ordinal(domain, range).unknown(unknown);
   };
 
-  initRange.apply(scale, arguments);
-
-  return scale;
+  return initRange.apply(scale, arguments);
 }
diff --git a/src/pow.js b/src/pow.js
@@ -40,9 +40,7 @@ export default function pow() {
     return copy(scale, pow()).exponent(scale.exponent());
   };
 
-  initRange.apply(scale, arguments);
-
-  return scale;
+  return initRange.apply(scale, arguments);
 }
 
 export function sqrt() {

diff --git a/src/symlog.js b/src/symlog.js
@@ -1,3 +1,5 @@
+import {format} from "d3-format";
+import nice from "./nice";
 import {linearish} from "./linear";
 import {copy, transformer} from "./continuous";
 import {initRange} from "./init";
@@ -15,13 +17,101 @@ function transformSymexp(c) {
 }
 
 export function symlogish(transform) {
-  var c = 1, scale = transform(transformSymlog(c), transformSymexp(c));
+  var c = 1, forward = transformSymlog(c), invert = transformSymexp(c),
+    scale = linearish(transform(forward, invert));
+
+  function rescale() {
+    transform(forward = transformSymlog(c), invert = transformSymexp(c));
+    return scale;
+  }
 
   scale.constant = function(_) {
-    return arguments.length ? transform(transformSymlog(c = +_), transformSymexp(c)) : c;
+    return arguments.length ? (c = +_, rescale()) : c;
+  };
+
+  function roundexp2_5(v) {
+    if (v == 0) return 0;
+    var r = v < 0;
+    if (r) v= -v;
+    var s = invert(v),
+        a = Math.log10(s),
+        a2 = Math.log10(s / 2),
+        a5 = Math.log10(s / 5),
+        b = -100 + Math.floor(100 + a),
+        b2 = -100 + Math.floor(100 + a2),
+        b5 = -100 + Math.floor(100 + a5),
+        c =  Math.pow(10, b);
+    if (b5 === b) c *= 5;
+    else if (b2 === b) c *= 2;
+    return r ? -c : c;
+  }
+
+  scale.ticks = function(count) {
+    var d = scale.domain(),
+        u = d[0],
+        v = d[d.length - 1],
+        r;
+
+    if (isNaN(n) || n <= 0 || n === Infinity) return [];
+
+    if (r = v < u) i = u, u = v, v = i;
+
+    var i = forward(u),
+        j = forward(v),
+        n = count == null ? 10 : +count,
+        z, zN = [], zP = [], m, s0, rs, rv, s;
+
+    var step = (j-i) / n;
+
+    // negatives
+    if (i < 0) {
+      m = Math.min(0, j);
+      s0 = -Infinity;
+      for (s = i; s < m; s += step) {
+        rs = roundexp2_5(s);
+        rv = forward(rs);
+        if (rv - s0 >= step && rv <= -step) {
+          zN.push(rs);
+          s0 = rv;
+        }
+      }
+    }
+
+    // 0
+    if (i * j <= 0 && n) zN.push(0);
+
+    // positives
+    if (j > 0) {
+      m = Math.max(0, i);
+      s0 = +Infinity;
+      for (s = j; s > m; s -= step) {
+        rs = roundexp2_5(s);
+        rv = forward(rs);
+        if (rv - s0 <= -step && rv >= step) {
+          zP.unshift(rs);
+          s0 = rv;
+        }
+      }
+    }
+
+    z = [...zN, ...zP];
+    return r ? z.reverse() : z;
+  };
+
+  scale.tickFormat = function(count, specifier) {
+    if (specifier === undefined) specifier = "~g";
+    if (typeof specifier !== "function") specifier = format(specifier);
+    return specifier;
+  };
+
+  scale.nice = function() {
+    return scale.domain(nice(scale.domain(), {
+      floor: function(x) { return roundexp2_5(forward(x)); },
+      ceil: function(x) { return roundexp2_5(forward(x)); }
+    }));
   };
 
-  return linearish(scale);
+  return scale;
 }
 
 export default function symlog() {