How Can I Re-scale An Array To A Range Of Values in Javascript?

Question

I'd like to re-scale a two dimensional array with a function where the min and max input range and min and max output range can be specified. For example, we want to re-scale the values 0 to 8 to 0 to 1.

const scale = (num, in_min, in_max, out_min, out_max) => {
    return (num - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;

var array_scaled = orignal_array.map(scale(num, 0, 8, 0, 1));

}

The code produces the following error: ReferenceError: num is not defined

What is the correct syntax to call the scale function from within map?

xpz · Accepted Answer · 2020-03-13 16:04:23Z

3

i guess the argument of map must be a function, i.e. :

var array_scaled = orignal_array.map(num=>scale(num, 0, 8, 0, 1));

answered Mar 13, 2020 at 16:04

xpz

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2 Comments

mmclean Over a year ago

thank you for solving my syntax error. However, the mapping returns Nan's instead of a new 2 dimensional array. Do you know why?

mmclean Over a year ago

I ended up doing this: array_scaled= Array.from(Array(n_dimension), () => new Array(m_dimension)); for (var row = 0; row < m_dimension; row++) { for (var col = 0; col < n_dimension; col++) { array_scaled[col][row] = this.scale(original_array[col][row], 0, 8, 0, 1); } }

Alan Cheung · Accepted Answer · 2020-03-13 16:03:04Z

0

Array.prototype.map() accepts a callback function as its first argument.

It looks like num is not defined as the current element of the array to the callback function scale()

Try var array_scaled = orignal_array.map(array_num => scale(array_num, 0, 8, 0, 1));

answered Mar 13, 2020 at 16:03

Alan Cheung

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