vis-utils

A collection of utility functions for helping with data visualization.

Development

Run tests

npm run test

Build the package

npm run build

Installing

If you use NPM, npm install vis-utils. Otherwise, download the latest release.

API Reference

• extentLimited
• extentMulti
• filterInRect
• filterInRectFromQuadtree
• findClosestSorted
• findClosestUnsorted
• findEqualSorted
• findEqualUnsorted
• rectContains
• rectIntersects
• rotate

# extentLimited(array, valueAccessor, minPercentile, maxPercentile)

Compute the extent (min and max) of an array, limiting the min and the max by the specified percentiles. Percentiles are values between 0 and 1.

Parameters

• array (Array) The array to iterate over
• [valueAccessor] (Function) How to read a value in the array (defaults to identity)
• [minPercentile] (Number) If provided, limits the min to this percentile value (between 0 and 1). If provided, the data is sorted by taking the difference of the valueAccessor results.
• [maxPercentile] (Number) If provided, limits the max to this percentile value (between 0 and 1). If provided, the data is sorted by taking the difference of the valueAccessor results.

Returns

(Array) The extent, limited by the min/max percentiles ([min, max])

# extentMulti(outerArray, valueAccessor, arrayAccessor, minPercentile, maxPercentile)

Compute the extent (min and max) across an array of arrays/objects

For example:

extentMulti([[4, 3], [1, 2]], d => d);
> [1, 4]

extentMulti([{ results: [{ x: 4 }, { x: 3 }] }, { results: [{ x: 1 }, { x: 2 }] }],
  d => d.x, array => array.results);
> [1, 4]

Parameters

• outerArray (Array) An array of arrays or objects
• [valueAccessor] (Function) How to read a value in the array (defaults to identity)
• [arrayAccessor] (Function) How to read an inner array (defaults to identity)
• [minPercentile] (Number) If provided, limits the min to this percentile value (between 0 and 1). If provided, the data is sorted by taking the difference of the valueAccessor results.
• [maxPercentile] (Number) If provided, limits the max to this percentile value (between 0 and 1). If provided, the data is sorted by taking the difference of the valueAccessor results.

Returns

(Array) The min and max across the arrays ([min, max])

# filterInRect(array, rect, x, y)

Filters the elements in the passed in array to those that are contained within the specified rectangle.

Parameters

• array (Array) The input array to filter
• rect (Number[][]) The rectangle, a pair of two points [[x, y], [x, y]]
• x (Function) Function that maps a point in the array to its x value (defaults to d => d[0])
• y (Function) Function that maps a point in the array to its y value (defaults to d => d[1])

Returns

(Array) The subset of the input array that is contained within the rectangle

# filterInRectFromQuadtree(array, rect, x, y)

Filters the elements in the passed in quadtree to those that are contained within the specified rectangle.

Parameters

• quadtree (Object) The input data as a d3-quadtree to filter
• rect (Number) The rectangle, a pair of two points [[x, y], [x, y]]
• x (Function) Function that maps a point in the array to its x value (defaults to d => d[0])
• y (Function) Function that maps a point in the array to its y value (defaults to d => d[1])

Returns

(Array) The subset of the input data that is contained within the rectangle

# findClosestSorted(array, value, accessor)

Helper function to compute distance and find the closest item Since it assumes the data is sorted, it does a binary search O(log n)

Parameters

• array (Array) the input array to search
• value (Number) the value to match against (typically pixels)
• [accessor] (Function) applied to each item in the array to get equivalent value to compare against (defaults to identity)

Returns

(Any) The item in the array that is closest to value

# findClosestUnsorted(array, value, accessor)

Helper function to compute distance and find the closest item Since it assumes the data is unsorted, it does a linear scan O(n).

Parameters

• array (Array) the input array to search
• value (Number) the value to match against (typically pixels)
• [accessor] (Function) applied to each item in the array to get equivalent value to compare against (defaults to identity)

Returns

(Any) The item in the array that is closest to value

# findEqualSorted(array, value, accessor)

Helper function to find the item that matches this value. Since it assumes the data is sorted, it does a binary search O(log n)

Parameters

• array (Array) the input array to search
• value (Number) the value to match against (typically pixels)
• [accessor] (Function) applied to each item in the array to get equivalent value to compare against (defaults to identity)

Returns

(Any) The item in the array that has this value or null if not found

# findEqualUnsorted(array, value, accessor)

Helper function to find the item that matches this value. Since it assumes the data is unsorted, it does a linear scan O(n).

Parameters

• array (Array) the input array to search
• value (Number) the value to match against (typically pixels)
• [accessor] (Function) applied to each item in the array to get equivalent value to compare against (defaults to identity)

Returns

(Any) The item in the array that has this value or null if not found

# rectContains(rect, point)

Determines if a point is inside a rectangle. The rectangle is defined by two points [[rx1, ry1], [rx2, ry2]].

• the upper left corner (rx1, ry1)
• the bottom right corner (rx2, ry2)

Note that it is assumed that the top Y value is less than the bottom Y value.

Parameters

• rect (Number[][]) The rectangle, a pair of two points [[x, y], [x, y]]
• point (Number[]) The point ([x, y])

Returns

(Boolean) true if the point is inside the rectangle, false otherwise

# rectIntersects(rect1, rect2)

Determines if two rectangles intersect. Here a rectangle is defined by its upper left and lower right corners.

Note that it is assumed that the top Y value is less than the bottom Y value.

Parameters

• rect1 (Number[][]) The first rectangle, a pair of two points [[x, y], [x, y]]
• rect2 (Number[][]) The second rectangle, a pair of two points [[x, y], [x, y]]

Returns

(Boolean) true if the rectangles intersect, false otherwise

# rotate(point, thetaRadians, origin)

Rotate a point ([x, y]) around an origin ([x, y]) by theta radians

Parameters

• point (Number[]) The point to rotate [x, y]
• thetaRadians (Number) How many radians to rotate the point around origin
• [origin] (Number[]) The origin to rotate around [x, y] (defaults to [0, 0])

Returns

(Number[]) The rotated point [x, y]