Get an index array from where using Linq - C# Unity3D

Question

I have an array of Vector3's from the polygon collider. I want to have an array of the indexes of all the Vector3's that are higher then a certain y.

    private void Awake()
    {
        polygonCollider2D = GetComponent<PolygonCollider2D>();
        float lowestY = polygonCollider2D.points.Min(x => x.y);
// So in the sentence below I want  to have a array of indexes instead of a array of vector3's.
        topPoints = polygonCollider2D.points.Where(x => x.y > lowestY).ToArray();
    }

Can I do this with Linq?

Take a look at the overload for Select that includes the index. — juharr
– juharr, Commented Mar 14, 2018 at 15:12

juharr · Accepted Answer · 2018-03-14 15:19:29Z

1

Yes you can use an overload of Select that includes the index like so

var topPointIndexes = polygonCollider2D.points
    .Select((p,i) => new{Point=p, Index=i})
    .Where(x => x.Point.y > lowestY)
    .Select(x => x.Index)
    .ToArray();

Another option is to just create the set of indexes up front

var points = polygonCollider2D.points;
var topPointIndexes = Enumerable.Range(0, points.Count())
    .Where(i => points[i].y > lowestY)
    .ToArray();

edited Mar 14, 2018 at 15:19

answered Mar 14, 2018 at 15:14

juharr

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Comments

Pac0 · Accepted Answer · 2018-03-14 15:20:33Z

0

The Select allows you to capture the index.

You can first select indexes and filter with the -1 'filter sentinel' value I used below,

topPointsIndexes = polygonCollider2D.points
    .Select((x, index) => (x.y > lowestY) ? index : -1) 
    .Where(i => i >= 0)
    .ToArray();

(or first expand the point and index together, and then filter, as juharr did in his answer)

edited Mar 14, 2018 at 15:20

answered Mar 14, 2018 at 15:14

Pac0

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anonymous-dev · Accepted Answer · 2018-03-14 15:22:50Z

0

indexesOfTopPoints = polygonCollider2D.points.Select((x, index) => index)
.Where(x => polygonCollider2D.points[x].y > lowestY).ToArray();

edited Mar 14, 2018 at 15:22

answered Mar 14, 2018 at 15:15

anonymous-dev

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Thiago Martins · Accepted Answer · 2018-03-14 15:28:57Z

0

Try it

topPoints = polygonCollider2D.points.Select((x, i) => new {obj = x, i = i}).Where(x => x.y > lowestY).Select(x => x.i).ToArray();

answered Mar 14, 2018 at 15:28

Thiago Martins

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