I have two arrays
x = [1 1 1 0 2 3 1 1]
y = [1 2 3 4 5 6 7 8]
How to calculate the sum of y's elements for all x(i) = 1 to get the result 1+2+3+7+8 ?
I have used for loop and if then method to calculate the sum value like this
if x(i) = 1 then sum = sum + y(i)
Have other methods to get the results (sum, average, count ...) ?
Thank you.
Since you only want to sum the numbers in y corresponding to 1s in x, but not 0s in x, you can multiply x * y which looks a bit cleaner than the If. Here are a few ways
Dim x = {1, 1, 1, 0, 0, 0, 1, 1}
Dim y = {1, 2, 3, 4, 5, 6, 7, 8}
' using a for loop
Dim sum1 As Integer = 0
For i = 0 To x.Length - 1
sum1 += If(x(i) = 1, 1, 0) * y(i)
Next
Console.WriteLine(sum1)
' using LINQ #1
Dim sum2 As Integer = x.Select(Function(i, index) If(i = 1, 1, 0) * y(index)).Sum()
Console.WriteLine(sum2)
' using LINQ #2
Dim sum3 As Integer = x.Zip(y, Function(x1, y1) If(x1 = 1, 1, 0) * y1).Sum()
Console.WriteLine(sum3)
' using LINQ #3
Dim sum4 As Integer = Enumerable.Range(0, x.Length).Sum(Function(i) If(x(i) = 1, 1, 0) * y(i))
Console.WriteLine(sum4)
Console.ReadLine()
x = [1 1 1 0 0 0 1 1] would have made that more clear? But I'll edit my answer.The For is very clear so I don't know why you wouldn't use it, but you can use LINQ for this as well:
Sub Main
Dim x = {1, 1, 1, 0, 2, 3, 1, 1}
Dim y = {1, 2, 3, 4, 5, 6, 7, 8}
Dim sum = y.Where(Function(v, i) x(i) = 1).Sum()
Console.WriteLine("Sum is {0}", sum)
End Sub
Prints
Sum is 21
