d3- Find max kay/value in nested arrays

## d3- Find max kay/value in nested arrays

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d3 max
d3 get max
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d3 max of multiple columns
d3 max dataset, function(d)

I have an array of 3 nested arrays, each containing 3 objects. What d3 syntax do I use to find the max value of data1 in all of the data?

Is it something like,

```function find_max(all_data, i){
return d3.max(all_data[i].data1)
}
```

Here's my data structure:

```all_data = [
[{data1:2, age:6},
{data1:4, age:5},
{data1:5, age:4}],

[{data1:7, age:2},
{data1:1, age:9},
{data1:0, age:8}],

[{data1:5, age:9},
{data1:6, age:9},
{data1:8, age:6}]
]
```

Basically, I want it to return 8. Thanks for the help!! I can't quite get it right.

We can use a mix of `d3.max` and `Array.map` operations:

```d3.max(all_data.map(d => d3.max(d.map(n => n.data1)))) // 8
```

This finds the max of each nested array using `d3.max` to find the max and a `map` operation to transform nested arrays of objects into an array of `data1` values (`[2, 4, 5]` for the first nested array).

```[{data1:2, age:6}, {data1:4, age:5}, {data1:5, age:4}].map(n => n.data1) // [2, 4, 5]
d3.max([{data1:2, age:6}, {data1:4, age:5}, {data1:5, age:4}].map(n => n.data1)) // 5
```

And with each sub-max, we find the global max using `d3.max` again.

```var all_data = [
[{data1:2, age:6},
{data1:4, age:5},
{data1:5, age:4}],

[{data1:7, age:2},
{data1:1, age:9},
{data1:0, age:8}],

[{data1:5, age:9},
{data1:6, age:9},
{data1:8, age:6}]
];

console.log(d3.max(all_data.map(d => d3.max(d.map(n => n.data1)))));```
`<script src="https://d3js.org/d3.v5.min.js"></script>`

Extent of extents · Issue #64 · d3/d3-array · GitHub, I propose to change d3.extent, d3.min, etc. to treat arrays differently (e.g. it's a common task to calculate extent of extents, and currently I see no The expectation is that you call d3.min and d3.max separately if you have nested arrays, such as: You'd by the value accessor to d3.min using d3.min.by:. # d3.max(iterable[, accessor]) · Source, Examples. Returns the maximum value in the given iterable using natural order. If the iterable contains no comparable values, returns undefined. An optional accessor function may be specified, which is equivalent to calling Array.from before computing the maximum value.

Probably the easiest way is to nest `d3.max()`:

```function findMax(data) {
return d3.max(data, arr =>    // return max of all nested max values
d3.max(arr, d => d.data1)   // return max of each nested array
);
}
```

The outer call to `d3.max()` uses its accessor function to get access to the maximum value of each nested array. The inner call will determine the maximum value for each nested array. For this purpose it defines an accessor function to return the `data1` property.

Have a look at the following working demo:

```const all_data = [
[{data1:2, age:6},
{data1:4, age:5},
{data1:5, age:4}],

[{data1:7, age:2},
{data1:1, age:9},
{data1:0, age:8}],

[{data1:5, age:9},
{data1:6, age:9},
{data1:8, age:6}]
];

function findMax(data) {
return d3.max(data, arr =>
d3.max(arr, d => d.data1)
);
}

console.log(findMax(all_data));```
`<script src="https://d3js.org/d3.v5.js"></script>`

Grouping Data, D3 includes the powerful d3.nest functionality to produce these groupings with a And that has been converted to a nice array of objects via our data reading powers Each object has a key property - which is what we used as the grouping value Here is another example where we get the average amount per person: The easiest way to work with D3 data arrays is to create simple arrays. For example, to create a stacked array, represent each stack in a stacked bar by the a comma separated value in a row per bar. state, males, females

You could map the inner `data1` values and get the max value and then take the result for the outer array.

```var all_data = [[{ data1: 2, age: 6 }, { data1: 4, age: 5 }, { data1: 5, age: 4 } ], [{ data1: 7, age: 2 }, { data1: 1, age: 9 }, { data1: 0, age: 8 }], [{ data1: 5, age: 9 }, { data1: 6, age: 9 }, { data1: 8, age: 6 }]],
maxData1 = Math.max(...all_data.map(a => Math.max(...a.map(({ data1 }) => data1))));

console.log(maxData1);```

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[PDF] Basic Concepts in Matlab, Michael G. Kay. Fitts Dept. of kay@ncsu.edu. January 2017 In Matlab, the case of a variable matters; e.g., the arrays a and create an array by first generating an array of zeros at the command line create a function mydist.m to determine the Euclidean A logical array of 1 (true) and 0 (false) values is returned as a. # d3.extent(array[, accessor]) Returns the minimum and maximum value in the given array using natural order. This is equivalent to calling d3.min and d3.max simultaneously. # d3.sum(array[, accessor]) Returns the sum of the given array. If the array is empty, returns 0.

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