I am trying to calculate velocity and acceleration, with the variable being the time t. I’d like to write these in vba, to make it faster, because later on I’ll need velocity and acceleration for several other calculations combined with different logical conditions. I would like the results to be printed in the worksheet, to double check during calculation if the results are realistic.

example of how it should like more or less

```
t vel a
0.002 39 -777
0.004 38.6 -802
0.006 35 -500
0.008 33.4 -400
0.01 32.1 -12297.1
```

So I have tried a few different things based on comments:

This first code example works fine I think from the results, but I still can see any of the results in between > so main question: any chance I can change the commend to write to the worksheet without changing much else?

The second code example is an attempt to write everything into arrays: I do understand the principle I think, but here the main error seems to be that my variable t is not getting generated properly and therefore the formulas are not calculated: can’t find the mistakes here and I would be grateful for some more help…

```
Kinematics Calculation
'Set t from 0 to 2 s with time step of 0.002s; Calculate Rot_vel until <= 0,
'Find index t_2 when Rot_vel <= 0
t = 0
Do
t = t + 0.002
Rot_vel = -10356# * t ^ 6 + 24130# * t ^ 5 - 19002# * t ^ 4 + 4933# * t ^ 3 +
362# * t ^ 2 - 213# * t + 39
Worksheets("test").Range(Cells(3, 2), Cells(1003, 2)) = Rot_vel
Loop Until Rot_vel <= 0
If Rot_vel <= 0 Then
t_2 = t
If t_2 > 0 Then
Debug.Print t_2
End If
End If
'Continue calculations for t 0 to t_2 with 0.002 steps
t = 0
Do
t = t + 0.002
A_rot = -62136# * t ^ 5 + 120650# * t ^ 4 - 76008# * t ^ 3 + 14797.8 * t
^ 2 + 723.26 * t - 212.7
Worksheets("test").Range(Cells(3, 3), Cells(1003, 3)).value = A_rot
L = MoI * Rot_vel / 1000
M = MoI * A_rot / 1000
Worksheets("test").Range(Cells(3, 8), Cells(1003, 8)).value = L
Worksheets("test").Range(Cells(3, 9), Cells(1003, 9)).value = M
G = L / t_2
Worksheets("test").Range(Cells(3, 10), Cells(1003, 10)).value = G
Loop Until t = t_2
```

Second version:

```
Kinematics Calculation
'Set t from 0 to 2 s with time step of 0.002s; Calculate Rot_vel until <= 0,
'Find index t_2 when Rot_vel <= 0
Dim arrCalc As Variant
Dim i As Integer
Dim j As Integer
ReDim arrCalc(i To 1003, j To 13)
For i = LBound(arrCalc, 2) To UBound(arrCalc, 2)
t = 0
Do
t = t + 0.002
arrCalc(i, 1) = t
arrCalc(i, 2) = -10356# * t ^ 6 + 24130# * t ^ 5 - 19002# * t ^ 4 + 4933#
* t ^ 3 + 362# * t ^ 2 - 213# * t + 39 'Rot_vel
Loop Until arrCalc(i, 2) < 0
Dim pos, val
val = 0
pos = Application.Match(val, arrCalc(i, 2), False)
pos = t_2
t = 0
Do
t = t + 0.002
arrCalc(i, 3) = -62136# * t ^ 5 + 120650# * t ^ 4 - 76008# * t ^ 3 +
14797.8 * t ^ 2 + 723.26 * t - 212.7
arrCalc(i, 8) = MoI * Rot_vel / 1000 'L
arrCalc(i, 9) = MoI * A_rot / 1000 'M
arrCalc(i, 10) = 1 / t_2 * L 'G
Loop Until t = t_2
Next i
With Worksheets("test")
.Cells(2, "A") = 0
.Cells(3, "A").Resize(UBound(arrCalc, 1), UBound(arrCalc, 2)) = Rot_vel
.Cells(2, "A").Resize(UBound(arrCalc, 1) + 1, 1) = t
'.Cells(3, "C").Resize(UBound(arrCalc, 1), UBound(arrCalc, 3)) = A_rot
End With
```

Your variables a_rot and rot_val don’t look to me like arrays but normal variables. Therefore, only one value is stored in them and of course you get only one value as an output.

I see two options: 1) You write all of your values into an array and then copy the array to the sheet. 2) You write each calculation line by line to the sheet. Number 1) is much much faster.

A solution could look something like this:

```
ReDim Array (Lines, Columns)
For each line
Array (line, Columns1) = Formula1
Array (line, Columns2) = Formula2
Array (line, Columns3) = Formula3
Next
```

### Answer：

Build a 2-D array with times and calculations then dump the results back onto the worksheet.

Sequential time is very prone to 15 significant digit floating point errors. These errors can be minimized with a form of datum dimensioning that creates all new entries relative to the original starting point instead of the previous value. The former method can have no error greater than a single calculation while the latter can compounding errors by carrying them into the next calculation.

```
Sub kinematicsCalculation()
Dim t As Double, start As Double, i As Long, arr As Variant
start = TimeSerial(0, 0, 0) 'start at 0 second mark
ReDim arr(1 To 1000, 1 To 2)
For i = LBound(arr, 1) To UBound(arr, 1)
arr(i, 1) = start + TimeSerial(0, 0, 2 * i) / 1000
'cannot attempt velocity calc without Rot_vel_i
arr(i, 2) = "<velocity calculation here>"
Next i
With Worksheets("sheet")
.Cells(2, "B") = start
.Cells(3, "B").Resize(UBound(arr, 1), UBound(arr, 2)) = arr
.Cells(2, "B").Resize(UBound(arr, 1) + 1, 1).NumberFormat = "[hh]:mm:ss.000"
End With
End Sub
```

Tags: excelexcel, oop, vba