hello,
I would like to draw a math function using DrawLine ().
This code use Pixel() displayed each 5° from 0 to 360°.
I post the code and output image in this topic.

dim yo(360),xo(360) as double
dim i as integer
dim yy, cfA,cfB,cfC,cfD,cfE as double

yy=(canvas1.Height/2) // to adjust X axe in half canvas.Haight

const deg2rad as double =0.017453292
cfA = 0.29
cfB= 3.68
cfC = -0.47
cfD=0.85
cfE = -0.387

For i = 0 To 360 step 5

xo(i) = i+1
yo(i) =cfA + cfB * sin(i*deg2rad) + cfC * cos(i*Deg2rad) +cfD * sin(2*i*Deg2rad)+cfE * cos(2*i*Deg2rad) //Function to draw
g.Pixel( xo(i)*1.45,yy-yo(i)*20)=color.Yellow // xo() and yo() are adjusted for the canvas (1.45,20)
//I want to use DrawLine method to connect pixels from 0 to 360

here - but i used path, hope you can use it in your xojo version

Sub Paint(g As Graphics, areas() As REALbasic.Rect) Handles Paint
g.DrawingColor = Color.Black
g.FillRectangle(0,0,g.Width,g.Height)
'---
Dim y,x As Double
Dim i As Integer
Dim yy, cfA,cfB,cfC,cfD,cfE As Double
yy=(canvas1.Height/2) // to adjust X axe in half canvas.Haight
Const deg2rad As Double = 0.017453292
cfA = 0.29
cfB = 3.68
cfC = -0.47
cfD = 0.85
cfE = -0.387
Var p As New GraphicsPath
For i = 0 To 360 Step 5
'Function to draw
x = i + 1.0
y = cfA + cfB * sin(i * deg2rad) + cfC * cos(i * Deg2rad) + cfD * sin(2.0 * i * Deg2rad) + cfE * cos(2.0 * i * Deg2rad)
'Scale and Translate
x = x * 1.45
y = yy - y * 20.0
If i = 0 Then
p.MoveToPoint(x, y) 'First
Else
p.AddLineToPoint(x, y)
End If
Next
g.DrawingColor = Color.Yellow
g.DrawPath(p, False)
End Sub

Sub Paint(g As Graphics, areas() As REALbasic.Rect) Handles Paint
g.DrawingColor = Color.Black
g.FillRectangle(0,0,g.Width,g.Height)
'---
Dim y, x As Double
Dim yy, cfA, cfB, cfC, cfD, cfE As Double
yy=(canvas1.Height/2) // to adjust X axe in half canvas.Haight
Const deg2rad As Double = 0.017453292
cfA = 0.29
cfB = 3.68
cfC = -0.47
cfD = 0.85
cfE = -0.387
Var p() As Point
For i As Integer = 0 To 360 Step 5
'Function to draw
x = i + 1.0
y = cfA + cfB * sin(i * deg2rad) + cfC * cos(i * Deg2rad) + cfD * sin(2.0 * i * Deg2rad) + cfE * cos(2.0 * i * Deg2rad)
'Scale and Translate
x = x * 1.45
y = yy - y * 20.0
p.Add New Point(x,y)
Next
g.DrawingColor = Color.Yellow
For i As Integer = 0 To p.LastIndex-1
'use a pair of points
g.DrawLine p(i).X, p(i).Y, p(i+1).X, p(i+1).Y
Next
End Sub

'Function to draw
x = i + 1.0
y = cfA + cfB * sin(i * deg2rad) + cfC * cos(i * Deg2rad) + cfD * sin(2.0 * i * Deg2rad) + cfE * cos(2.0 * i * Deg2rad)
'Scale and Translate
x = x * 1.45
y = yy - y * 20.0
p.Add New Point(x,y)

Next

g.ForeColor = Color.Yellow

For i As Integer = 0 To p.LastIndex-1
'use a pair of points
g.DrawLine p(i).X, p(i).Y, p(i+1).X, p(i+1).Y
Next

what is the problem to create a new class with x,y property?
.LastIndex-1 could be Ubound ( p ) -1 in older xojo
unfortunately array.add is also something new …
maybe just use a x and y array with the count you need

you need the data for 2 angles because you will draw a line from as example 0 degree to 5 degree.
the next line is from 5 degree to 10 degree.
if you have a point list it would have index 0,1,2 for the degree 0,5,10 (if you collect data in 5 degree steps.)

It’s not necessary to save all of the points in an array. It’s only necessary to save the previous point. This is what I usually use to draw connected points:

lastX = 0
lastY = myFunction(lastX)
for x as double = 1 to maxX
y=myFunction(x)
g.drawline(lastX,lastY,x,y)
lastX=x
lastY=y
next

lastX = 0
lastY = myFunction(lastX)
for x as double = 1 to maxX
y=myFunction(x)
g.drawline(lastX,lastY,x,y)
lastX=x
lastY=y
next

[/quote]
>
Dim y, x As Double
Dim yy, cfA, cfB, cfC, cfD, cfE As Double
dim i as integer
yy=(canvas1.Height/2) // to adjust X axe in half canvas.Haight
Const deg2rad As Double = 0.017453292
cfA = 0.29
cfB = 3.68
cfC = -0.47
cfD = 0.85
cfE = -0.387
dim lastX,lastY,maxX as double
maxX = 360
lastX = 0
lastY =cfA + cfB * sin(lastx*deg2rad) + cfC * cos(lastx*deg2rad) +cfD * sin(2*deg2rad)+cfE *
cos(2*lastx*Trigo.rad) // myFunction(lastX)
for i = 1 to maxX
y= cfA + cfB * sin(i*deg2rad) + cfC * cos(i*deg2rad) +cfD * sin(2*i*deg2rad)+cfE * cos(2*i*deg2rad)
//myFunction(x)
g.ForeColor = color.green
g.drawline(lastX,lastY,x,y)
lastX=i
lastY=y
next
Unfortunately does not run.
As i explain in the beginning of this topic, want to connect the points by line as show in screenshot.
MarkusR gives a good solution, but my xojo 2015r1 does not support a newest features.

Sub Constructor(x as double, y as double)
me.X=round(x) //or directly x if no rounding is needed
me.Y=round(y)
End sub

Dim p() As DJpoint

For i = 0 To 360 Step 5

'Function to draw
x = i + 1
y = cfA + cfB * sin(i * deg2rad) + cfC * cos(i * Deg2rad) + cfD * sin(2.0 * i * Deg2rad) + cfE * cos(2.0 * i * Deg2rad)
'Scale and Translate
x = x * 1.71
y = yy - y * 20.0
//p.Add New DJPoint(x,y)
p.Append New DJPoint(x,y)

Next

g.ForeColor = Color.Yellow

For i = 0 To p.Ubound-1
'use a pair of points
g.ForeColor = rgb(0,160,0)
g.DrawLine p(i).X, p(i).Y, p(i+1).X, p(i+1).Y
Next

MarkusR, this code is yours adapted to xojo 2015r1.
It’s running well.

I would like to continue in same topic, i have wrote code to convert mouse coordinates to canvas coordinates (curve).
i discover that with tooltip control it is possible to show the values when cursor is moving on the curve.
Any example or link ?

If ChkCursor.State =checkBox.CheckedStates.Checked then

LbltoolTip.Left=x - (lbltoolTip.Width/2 )+50 // convert Mouse.X to CC
LblToolTip.Top=y+ (lbltoolTip.Height+60) // convert Mouse.Y to dev
if (mX <0 or mY < 0 or mX > cnvCompas.Width or mY>cnvCompas.Height) then
LblToolTip.Visible =false
else
LblTooltip.Visible= true
end if
LblToolTip.text = "CC:" +format(cc,"000.0") +"°" +", dev: " +format(dv,"-#.0")+"°"

end if

CnvCompas.invalidate

As is shown on the attached screenshot mouse pointer display a correct values.
But the lblToolTip.text is flashing to white color when mouse cursor move.