Select element corresponding to maximum/minimum value in different column

Question

I am trying to find the value corresponding to maximum value in another column in my array, but get an error with the present code saying Unable to cast object of type WhereSelectArrayIterator2[Main.AllClasses.MaxMin,System.Int32] to type 'System.IConvertible'.`

I am assigning a list of type MaxMin to an array and then trying to calculate the maxima and its corresponding element in the second column. Here's the code:

MaxMin finalMax = new MaxMin();
if (maxima.Count != 0)
{
      MaxMin[] maxArray = maxima.ToArray();
      finalMax.val = maxArray.Select(x => x.val).Max();
      finalMax.cnt = Convert.ToInt32(maxArray.Where(x => x.val.Equals(finalMax.val)).Select(x => x.cnt));
}

Here's the full code:

public MaxMin Maxima(float[] values, MaxMin drop)
    {
        float[] T = new float[5] { 0, 0, 0, 0, 0 };
        float[] dT = new float[4] { 0, 0, 0, 0 };
        int count = 0;
        List<MaxMin> maxima = new List<MaxMin>();


        count = values.Length;


        try
        {
            for (int i = 99; i < count - 100; i++)
            {
                MaxMin max = new MaxMin();

                T[0] = values[i - 1];
                T[1] = values[i];
                T[2] = values[i + 1];
                T[3] = values[i + 2];
                T[4] = values[i + 3];

                dT[0] = T[1] - T[0];
                dT[1] = T[2] - T[1];
                dT[2] = T[3] - T[2];
                dT[3] = T[4] - T[3];


                if (i > drop.cnt)     //cutoff time above which calculation of minima will be initiated
                {
                    if (dT[1] > 0 && dT[3] < 0)
                    {
                        float[] diff = new float[8] { 0, 0, 0, 0, 0, 0, 0, 0 };
                        diff[0] = (values[i + 1] - values[i - 19]);
                        diff[1] = (values[i + 1] - values[i + 19]);
                        diff[2] = (values[i + 1] - values[i - 49]);
                        diff[3] = (values[i + 1] - values[i + 49]);
                        diff[4] = (values[i + 1] - values[i - 69]);
                        diff[5] = (values[i + 1] - values[i + 69]);
                        diff[6] = (values[i + 1] - values[i - 99]);
                        diff[7] = (values[i + 1] - values[i + 99]);

                        if (diff[0] < 20 && diff[1] < 20 && diff[2] < 20 && diff[3] < 20 && diff[2] > 0 && diff[3] > 0 && diff[4] > 0.5 && diff[5] > 0.5 && diff[6] > 2 && diff[7] > 2)
                        {
                            max.cnt = i + 1;
                            max.val = values[i + 1];
                            maxima.Add(max);
                        }

                    }
                }
            }


            MaxMin finalMax = new MaxMin();

            if (maxima.Count != 0)
            {
                MaxMin[] maxArray = maxima.ToArray();
                finalMax.val = maxArray.Select(x => x.val).Max();
                finalMax.cnt = Convert.ToInt32(maxArray.Where(x => x.val.Equals(finalMax.val)).Select(x => x.cnt));
            }

            else
            {
                finalMax.val = values.Max();
                finalMax.cnt = Array.IndexOf(values, values.Max());
            }


            return finalMax;
        }

        catch (Exception ex)
        {
            throw ex;
        }
  }

You may need to do something like finalMax.val = maxArray.Select(x => x.val).Max().<some field>; — Amarnath R Shenoy
– Amarnath R Shenoy, Commented Mar 20, 2014 at 3:58

MarcinJuraszek · Accepted Answer · 2014-03-20 03:57:57Z

1

You're trying to convert results of Select method call, which returns IEnumerable<T>, to int. That's not gonna work.

Use First instead of Where/Select:

finalMax.cnt = maxArray.First(x => x.val.Equals(finalMax.val)).cnt;

answered Mar 20, 2014 at 3:57

MarcinJuraszek

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