how to replace each element (of struct type) with another element in an array using Linq?

Question

I have a Point struct:

public struct Point
{
    public Point(double x, double y, double z)
    {
        X = x;
        Y = y;
        Z = z;
    }

    public double X;
    public double Y;
    public double Z;
}

then in the following code, I am creating an array of points and then dividing each points by a value 2

//Create a test array of Points
Point[] testPointArray = new Point[2];
testPointArray[0] = new Point(2, 4, 8);
testPointArray[1] = new Point(6, 12, 24);

//Divide by 2
testPointArray = testPointArray.Select(point => point = new Point(point.X / 2, point.Y / 2, point.Z / 2)).ToArray();

Question: In the above code, I am using the new operator to replace each point with a newly created point. How can I directly make changes in the existing point (i.e. avoid creating new points)? I tried to do the following code, but the syntax is wrong:

testPointArray = testPointArray.Select(point =>
{
    point.X = point.X / 2;
    point.Y = point.Y / 2;
    point.Z = point.Z / 2;
}).ToArray();

Answer 1

testPointArray = testPointArray.Select(point =>
{
    point.X /= 2;
    point.Y /= 2;
    point.Z /= 2;
    return point;
}).ToArray();

In your example your lambda returns nothing - adding return point returns the mutated point for your select.

I agree with jalsh's comment that you should create new points, something like:

testPointArray = testPointArray.Select(point => new Point(point.X / 2, point.Y / 2, point.Z / 2))
            .ToArray();

Answer 2

I usually do stuff like this using matplotlib.pyplot.fill_between, with a low alpha (opacity of the shadow) and given the lower and upper bounds of the shaded area, which I'm assuming you could calculate from the frequency.