How can I write code that makes a spiral? - vba

Question

I just started learning to programming in Excel VBA, and I have a problem.
I want to draw a spiral with a program, but a can not solve it well.
I would like to use for and do until and do while cycles only.
Here is my code:
Sub spiral()
For i = 1 To 16
xmm = xmm - 1
ymm = ymm - 1
Do Until xp = i
xp = xp + 1
Cells(5 + xp, 5) = i
Loop
Do Until yp = i
yp = yp + 1
Cells(5 + xp, 5 + yp) = i + 1
Loop
Do Until xm > xp
xm = xm + 1
Cells(5 + xp + i * xmm, 5 + yp) = i + 2
Loop
Do Until ym > yp
ym = ym + 1
Cells(5 + xp + xmm, 5 + yp + i * ymm) = i + 3
Loop
Next i
End Sub
Thanks!

Answer 1

I can't think of any practical reason you'd need this, but that said, I'm often wasting time messing around with odd tasks "just to see if I can." 😊
Access VBA Circles
Recently a spiral was a self-assigned challenge I played with in SQL, although it originated with a circle in Access VBA from another useless project of mine:
Access World : Making an Analog Clock on an MS Access Form
This taught me a number of concepts including how to draw a circle on a grid.
Drawing a circle is almost the identical process as drawing the hands on that clock. If, rather than drawing the whole line of the clock hand, I instead draw only the tip of it (aka, the radius), all the way around, the 360°, then I have a circle.
SQL Circle
Say that ten times fast!
Then one day I wondered how hard it would be to convert the circle code to SQL Server, exploiting the graphing feature of the Stack Exchange Data Explorer (SEDE). A graph is drawn on a grid, so it's the same concept.
Here is one of several results (again, all useless):
SEDE : Draw Random Circles on chart
Click Run Query and then when it's finished calculating click the Graph tab. (You'll also need to either login with your Stack Exchange ID, or do the captcha.) There are various constants you can play with in the user prompts (below the SQL).
SQL Spiral
Then at some point I wondered about spirals.
(...but probably should have been time for me to get a life? Naaaa, lol)
A spiral is simply a modified circle except the radius decreases (or increases) as you progress around the circumference -- and you don't stop at 360° -- instead just keep going and going, and continually changing the radius at a steady rate.
SEDE : Draw a spiral
Again, click Run Query and then when it's finished calculating click the Graph tab. (You'll also need to either login with your Stack Exchange ID, or do the captcha.) There are various constants you can play with in the user prompts (below the SQL).
Spiral in Excel
I'm not going to waste any more time on spirals today, but if I was going to draw one in Excel worksheet cells, I would resize all cells on the worksheet to a tiny square grid (maybe width=1, height=10), and then I would borrow the code from the SQL example, adapting it to Excel (which woudn't take much work).
The Access VBA example may be more confusing to adapt since there a lot of programmatic manipulation of controls going on (which can't be done at runtime).
Or, the Access example could be duplicated in Excel using controls (ie., lines) instead of the grid method you were trying so far.
More Information:
Wikipedia : Midpoint Circle Algorithm
rosettacode : Midpoint circle algorithm examples (code in 39 languages)
tutsPlus.com : Working with circles/spirals
Math Overflow : How to spiral coordinates in an outward pattern on 2D grid?

Answer 2

Base on some answers from this thread (Looping in a spiral), I've managed to come with this solution
Sub spiral()
x = 0
y = 0
d = 1
m = 1
i = 1
j = 1
Do While i < 6
Do While 2 * x * d < m
Cells(x + 5, y + 5).Value = j
x = x + d
j = j + 1
Loop
Do While 2 * y * d < m
Cells(x + 5, y + 5).Value = j
y = y + d
j = j + 1
Loop
d = -1 * d
m = m + 1
i = i + 1
Loop
End Sub
Not sure if it is something that you are looking for thou, as you didn't specify the exact output that you want to achieve.