diff --git a/API.md b/API.md
index 961dd579..e7902446 100644
--- a/API.md
+++ b/API.md
@@ -331,25 +331,26 @@ Color ramps and palettes for quantitative, ordinal and categorical scales.
 * [d3.interpolateRainbow](https://github.com/d3/d3-scale-chromatic/blob/v3.0.0/README.md#interpolateRainbow) - the “less-angry” rainbow
 * [d3.interpolateSinebow](https://github.com/d3/d3-scale-chromatic/blob/v3.0.0/README.md#interpolateSinebow) - the “sinebow” smooth rainbow
 
-## [Contours (d3-contour)](https://github.com/d3/d3-contour/tree/v3.0.2)
+## [Contours (d3-contour)](https://github.com/d3/d3-contour/tree/v3.1.0)
 
 Compute contour polygons using marching squares.
 
-* [d3.contours](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#contours) - create a new contour generator.
-* [*contours*](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#_contours) - compute the contours for a given grid of values.
-* [*contours*.contour](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#contours_contour) - compute a contour for a given value.
-* [*contours*.size](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#contours_size) - set the size of a contour generator.
-* [*contours*.smooth](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#contours_smooth) - set whether or not the generated contours are smoothed.
-* [*contours*.thresholds](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#contours_thresholds) - set the thresholds of a contour generator.
-* [d3.contourDensity](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#contourDensity) - create a new density estimator.
-* [*density*](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#_density) - estimate the density of a given array of samples.
-* [*density*.x](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#density_x) - set the *x* accessor of the density estimator.
-* [*density*.y](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#density_y) - set the *y* accessor of the density estimator.
-* [*density*.weight](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#density_weight) - set the *weight* accessor of the density estimator.
-* [*density*.size](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#density_size) - set the size of the density estimator.
-* [*density*.cellSize](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#density_cellSize) - set the cell size of the density estimator.
-* [*density*.thresholds](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#density_thresholds) - set the thresholds of the density estimator.
-* [*density*.bandwidth](https://github.com/d3/d3-contour/blob/v3.0.2/README.md#density_bandwidth) - set the bandwidth of the density estimator.
+* [d3.contours](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#contours) - create a new contour generator.
+* [*contours*](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#_contours) - compute the contours for a given grid of values.
+* [*contours*.contour](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#contours_contour) - compute a contour for a given value.
+* [*contours*.size](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#contours_size) - set the size of a contour generator.
+* [*contours*.smooth](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#contours_smooth) - set whether or not the generated contours are smoothed.
+* [*contours*.thresholds](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#contours_thresholds) - set the thresholds of a contour generator.
+* [d3.contourDensity](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#contourDensity) - create a new density estimator.
+* [*density*](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#_density) - estimate the density of a given array of samples.
+* [*density*.x](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#density_x) - set the *x* accessor of the density estimator.
+* [*density*.y](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#density_y) - set the *y* accessor of the density estimator.
+* [*density*.weight](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#density_weight) - set the *weight* accessor of the density estimator.
+* [*density*.size](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#density_size) - set the size of the density estimator.
+* [*density*.cellSize](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#density_cellSize) - set the cell size of the density estimator.
+* [*density*.thresholds](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#density_thresholds) - set the thresholds of the density estimator.
+* [*density*.bandwidth](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#density_bandwidth) - set the bandwidth of the density estimator.
+* [*density*.contours](https://github.com/d3/d3-contour/blob/v3.1.0/README.md#density_contours) - compute density contours.
 
 ## [Voronoi Diagrams (d3-delaunay)](https://github.com/d3/d3-delaunay/tree/v6.0.2)
 
diff --git a/yarn.lock b/yarn.lock
index be4145f0..6b2d7939 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -53,23 +53,23 @@
   integrity sha512-ZnQMnLV4e7hDlUvw8H+U8ASL02SS2Gn6+9Ac3wGGLIe7+je2AeAOxPY+izIPJDfFDb7eDjev0Us8MO1iFRN8hA==
 
 "@jridgewell/gen-mapping@^0.3.0":
-  version "0.3.1"
-  resolved "https://registry.yarnpkg.com/@jridgewell/gen-mapping/-/gen-mapping-0.3.1.tgz#cf92a983c83466b8c0ce9124fadeaf09f7c66ea9"
-  integrity sha512-GcHwniMlA2z+WFPWuY8lp3fsza0I8xPFMWL5+n8LYyP6PSvPrXf4+n8stDHZY2DM0zy9sVkRDy1jDI4XGzYVqg==
+  version "0.3.2"
+  resolved "https://registry.yarnpkg.com/@jridgewell/gen-mapping/-/gen-mapping-0.3.2.tgz#c1aedc61e853f2bb9f5dfe6d4442d3b565b253b9"
+  integrity sha512-mh65xKQAzI6iBcFzwv28KVWSmCkdRBWoOh+bYQGW3+6OZvbbN3TqMGo5hqYxQniRcH9F2VZIoJCm4pa3BPDK/A==
   dependencies:
-    "@jridgewell/set-array" "^1.0.0"
+    "@jridgewell/set-array" "^1.0.1"
     "@jridgewell/sourcemap-codec" "^1.4.10"
     "@jridgewell/trace-mapping" "^0.3.9"
 
 "@jridgewell/resolve-uri@^3.0.3":
-  version "3.0.7"
-  resolved "https://registry.yarnpkg.com/@jridgewell/resolve-uri/-/resolve-uri-3.0.7.tgz#30cd49820a962aff48c8fffc5cd760151fca61fe"
-  integrity sha512-8cXDaBBHOr2pQ7j77Y6Vp5VDT2sIqWyWQ56TjEq4ih/a4iST3dItRe8Q9fp0rrIl9DoKhWQtUQz/YpOxLkXbNA==
+  version "3.0.8"
+  resolved "https://registry.yarnpkg.com/@jridgewell/resolve-uri/-/resolve-uri-3.0.8.tgz#687cc2bbf243f4e9a868ecf2262318e2658873a1"
+  integrity sha512-YK5G9LaddzGbcucK4c8h5tWFmMPBvRZ/uyWmN1/SbBdIvqGUdWGkJ5BAaccgs6XbzVLsqbPJrBSFwKv3kT9i7w==
 
-"@jridgewell/set-array@^1.0.0":
-  version "1.1.1"
-  resolved "https://registry.yarnpkg.com/@jridgewell/set-array/-/set-array-1.1.1.tgz#36a6acc93987adcf0ba50c66908bd0b70de8afea"
-  integrity sha512-Ct5MqZkLGEXTVmQYbGtx9SVqD2fqwvdubdps5D3djjAkgkKwT918VNOz65pEHFaYTeWcukmJmH5SwsA9Tn2ObQ==
+"@jridgewell/set-array@^1.0.1":
+  version "1.1.2"
+  resolved "https://registry.yarnpkg.com/@jridgewell/set-array/-/set-array-1.1.2.tgz#7c6cf998d6d20b914c0a55a91ae928ff25965e72"
+  integrity sha512-xnkseuNADM0gt2bs+BvhO0p78Mk762YnZdsuzFV018NoG1Sj1SCQvpSqa7XUaTam5vAGasABV9qXASMKnFMwMw==
 
 "@jridgewell/source-map@^0.3.2":
   version "0.3.2"
@@ -80,14 +80,14 @@
     "@jridgewell/trace-mapping" "^0.3.9"
 
 "@jridgewell/sourcemap-codec@^1.4.10":
-  version "1.4.13"
-  resolved "https://registry.yarnpkg.com/@jridgewell/sourcemap-codec/-/sourcemap-codec-1.4.13.tgz#b6461fb0c2964356c469e115f504c95ad97ab88c"
-  integrity sha512-GryiOJmNcWbovBxTfZSF71V/mXbgcV3MewDe3kIMCLyIh5e7SKAeUZs+rMnJ8jkMolZ/4/VsdBmMrw3l+VdZ3w==
+  version "1.4.14"
+  resolved "https://registry.yarnpkg.com/@jridgewell/sourcemap-codec/-/sourcemap-codec-1.4.14.tgz#add4c98d341472a289190b424efbdb096991bb24"
+  integrity sha512-XPSJHWmi394fuUuzDnGz1wiKqWfo1yXecHQMRf2l6hztTO+nPru658AyDngaBe7isIxEkRsPR3FZh+s7iVa4Uw==
 
 "@jridgewell/trace-mapping@^0.3.9":
-  version "0.3.13"
-  resolved "https://registry.yarnpkg.com/@jridgewell/trace-mapping/-/trace-mapping-0.3.13.tgz#dcfe3e95f224c8fe97a87a5235defec999aa92ea"
-  integrity sha512-o1xbKhp9qnIAoHJSWd6KlCZfqslL4valSF81H8ImioOAxluWYWOpWkpyktY2vnt4tbrX9XYaxovq6cgowaJp2w==
+  version "0.3.14"
+  resolved "https://registry.yarnpkg.com/@jridgewell/trace-mapping/-/trace-mapping-0.3.14.tgz#b231a081d8f66796e475ad588a1ef473112701ed"
+  integrity sha512-bJWEfQ9lPTvm3SneWwRFVLzrh6nhjwqw7TUFFBEMzwvg7t7PCDenf2lDwqo4NQXzdpgBXyFgDWnQA+2vkruksQ==
   dependencies:
     "@jridgewell/resolve-uri" "^3.0.3"
     "@jridgewell/sourcemap-codec" "^1.4.10"
@@ -386,9 +386,9 @@ d3-chord@3:
   integrity sha512-zg/chbXyeBtMQ1LbD/WSoW2DpC3I0mpmPdW+ynRTj/x2DAWYrIY7qeZIHidozwV24m4iavr15lNwIwLxRmOxhA==
 
 d3-contour@3:
-  version "3.0.2"
-  resolved "https://registry.yarnpkg.com/d3-contour/-/d3-contour-3.0.2.tgz#eff71df949788ae5803b05a24cbb1f527c3ada65"
-  integrity sha512-n0zP1c2sqsdZEGStDhYXpzihrzmQHFcKXsXatX2jc+uJx9Va0kKB5qepJ9V0hbgFWM+05wrJ0Npo+dXKP3GZ8Q==
+  version "3.1.0"
+  resolved "https://registry.yarnpkg.com/d3-contour/-/d3-contour-3.1.0.tgz#708484a5d89be9558dfdda4a95b3df2fdebb65ab"
+  integrity sha512-vV3xtwrYK5p1J4vyukr70m57mtFTEQYqoaDC1ylBfht/hkdUF0nfWZ1b3V2EPBUVkUkoqq5/fbRoBImBWJgOsg==
   dependencies:
     d3-array "2 - 3"