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DecemberDream opened this issue Nov 29, 2021 · 2 comments
Closed

Advanced Array Indexing #89

DecemberDream opened this issue Nov 29, 2021 · 2 comments

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@DecemberDream
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Is advanced array indexing notation available? I tried implementing the second example from the NumPy documentation about array indexing, however, each time I try to run it, I get the following error:

System.ArgumentException: 'Invalid slice notation'

My code is:

NDarray test = np.array(new int[,] { { 0, 1, 2 }, { 3, 4, 5 }, { 6, 7, 8 }, { 9, 10, 11 } });
NDarray rows = np.array(new int[,] { { 0, 0 }, { 3, 3 } });
NDarray cols = np.array(new int[,] { { 0, 2 }, { 0, 2 } });
printNDarray2D(test[$"{rows}, {cols}"]); // System.ArgumentException: 'Invalid slice notation'
// should return
// [[0, 2],
//  [9, 11]]

Where the printNDarray2D-function is:

public static void printNDarray2D(NDarray array)
{
    for (int i = 0; i < array.len; ++i)
    {
        for(int j = 0; j < array[0].len; ++j)
        {
            Console.Write("{0,10} ", ((double)array[i][j]).ToString("0.00000"));
        }

        Console.WriteLine();
    }

    Console.WriteLine();
}

Is there a way to index an NDarray using another NDarray? Am I missing something?
henon added a commit that referenced this issue Dec 1, 2021
@henon
Test case for #89
4081040
@henon
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henon commented Dec 1, 2021

yes:

        [TestMethod]
        public void IssueByDecemberDream2()
        {
            NDarray test = np.array(new int[,] { { 0, 1, 2 }, { 3, 4, 5 }, { 6, 7, 8 }, { 9, 10, 11 } });
            NDarray rows = np.array(new int[,] { { 0, 0 }, { 3, 3 } });
            NDarray cols = np.array(new int[,] { { 0, 2 }, { 0, 2 } });

            var b = test[rows, cols];
            // should return
            // [[0, 2],
            //  [9, 11]]
            Assert.AreEqual("array([[ 0,  2],\n       [ 9, 11]])", b.repr);
        }

@henon henon closed this as completed Dec 1, 2021
@JimXu1989
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JimXu1989 commented Feb 3, 2022 •
edited by henon
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The code only return a single value, b = {0}, not a matrix.

Edit by Henon: this has been moved to issue #95

@henon henon mentioned this issue Feb 3, 2022
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3 participants
@henon @JimXu1989 @DecemberDream