Try to input data on a specific row of an Array - vba

Question

I have crated an Array with 500 rows and 10 columns. I am trying to generate an array of Signal strength using the radar range equation. I want to detect two targets at two ranges and I am putting them in the array at a specific point. I have 2 If statements nested within 2 for loops. The for loops work properly, I can't figure out where my If statements are wrong though. All of the values are correct (Hence the msgboxs for the values)
I have tried moving the Signal(i, j) = 0 into an If statement but I wasn't sure how to set the bounds since it is at every other points besides row 50 and 250.
Sub Generate_Power_Amplitude()
'/////////////////////Basic Parameters////////////////////////////
'/////////////////////Step 1//////////////////////////////////////
' Input the parameters of the Radar Range Equation
TotalPower = 10000 '(Watts)
Gain = 3162.27766 '(35 dB of gain)
Wavelength = 0.3 '(meters)
RCS = 15 '(meters^2)
RangeToTarget = 35000 '(meters)
PulseWidth = 1.67 * 10 ^ -6 '(seconds)
Bandwidth = 6 * 10 ^ 5 '(Hertz)
RangeBins = 1 * 10 ^ 3 '(meters)
PRI = 1 * 10 ^ -4 '(seconds)
PRF = 1 * 10 ^ 4 '(Hertz)
PRIDistance = 60000 '(meters)
'//////////////////Targets/////////////////////////////////////////////
'//////////////////Step 2//////////////////////////////////////////////
' Define how many targets and their distance
Target1 = 25000 '(meters)
Target2 = 125000 '(meters)
'/////////////////Operations//////////////////////////////////////////
RadarRangeNumerator = TotalPower * Gain ^ 2 * Wavelength ^ 2 * RCS
RadarRangeDenomenator = (4 * 3.1415926) ^ 3 * RangeToTarget ^ 4
RelativePower = RadarRangeNumerator / RadarRangeDenomenator
PowerAmplitude = RelativePower ^ 0.5
RelativePower1 = RadarRangeNumerator / ((4 * 3.1415926) ^ 3 * Target1 ^ 4)
RelativePower2 = RadarRangeNumerator / ((4 * 3.1415926) ^ 3 * Target2 ^ 4)
PowerAmp1 = RelativePower1 ^ 0.5
PowerAmp2 = RelativePower2 ^ 0.5
Dim Signal(500, 10)
For i = 1 To 500
For j = 1 To 10
If i = 50 Then
Signal(50, j) = PowerAmp1
ElseIf i = 250 Then
Signal(250, j) = PowerAmp2
End If
Signal(i, j) = 0
Next j
Next i
MsgBox Signal(50, 1)
MsgBox Signal(250, 1)
End Sub
I got the msgboxes to give the right values and this is the new For Loop, there is a comment below, as I said I feel this will eventually break and if there is a right way to do this let me know.
Dim Signal(500, 10)
For i = 1 To 500
For j = 1 To 10
If i = 500 Then
Signal(50, j) = PowerAmp1
Signal(250, j) = PowerAmp2
End If
Signal(i, j) = 0
Next j
Next i

Answer 1

This may be too simple of an answer but it seems like you just need to loop using the Ubound and Lbound tools. Here's an example with your code where you set the limits based on the Array size:
Dim Signal(500, 10)
For i = Lbound(Signal,1) To Ubound(Signal,1)
For j = LBound(Signal,2) To UBound(Signal,2)
If i = Ubound(Signal,1) Then
'This part confuses me:
Signal(50, j) = PowerAmp1
Signal(250, j) = PowerAmp2
End If
Signal(i, j) = 0
Next j
Next i

Answer 2

If all you ever want to do is insert the values for 50 and 250 into an array, then you don't need to set all the values to zero. In VBA, all variable values are initialized to zero including elements of an array. So this will produce the exact same result as your code:
Dim Signal(1 To 500, 1 To 10)
Signal(50, j) = PowerAmp1
Signal(250, j) = PowerAmp2
And, by the way, notice that I'm specifically stating the dimension range of the array. VBA will default to a zero-based array -- meaning your definition produced an array from 0 to 500, i.e. 501 elements.
#PGSystemTester is exactly correct in relating your loop bounds directly to the array bounds. This is a very common practice and can save you lots of heartache later on.
Dim Signal(1 To 500, 1 To 10)
For i = LBound(Signal, 1) To UBound(Signal, 1)
For j = LBound(Signal, 2) To UBound(Signal, 2)
If i = 500 Then
Signal(50, j) = PowerAmp1
Signal(250, j) = PowerAmp2
End If
Signal(i, j) = 0
Next j
Next i
Your next step may be to calculate the power at a series of stepped ranges to each target. Keep in mind that to define a variable number of steps -- array elements in this case -- you'll have to use ReDim
Const RANGE_STEPS As Long = 1000
Dim Signal As Variant
ReDim Signal(1 To RANGE_STEPS, 1 To 10)
If you're using the UBound and LBound functions, your loop remains exactly the same.