How to calculate the straight line when using the logarithmic scale?

AFL Programming
1

How to calculate the straight line when using the logarithmic scale?

Using the LineArray function and plotting on the logarithmic scale I get the blue line,

How do I get the red line as a result ?

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Plot( C, "Close", colorDefault, styleNoTitle | GetPriceStyle() ); 

bi = BarIndex();
llb = bi - LowestBars(Low);
hhb = bi - HighestBars(High);
ll = Lowest(Low);
hh = Highest(High);

//y = LineArray(LastValue(llb), log(LastValue(ll)), LastValue(hhb), log(LastValue(hh)));
y = LineArray(LastValue(llb), LastValue(ll), LastValue(hhb), LastValue(hh), 1);

Plot(y, "y", colorBlue);
2

Try this: ln(y) = a + bx where a = y intercept and b = slope of line

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3

You could replace your LineArray and Plot calls with:

GfxSetCoordsMode(1);
GfxMoveTo(LastValue(llb), LastValue(ll));
GfxLineTo(LastValue(hhb), LastValue(hh));
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4

well, this would draw the line as I expected,
but I would also like to have an array of y values.
What I am looking for is the formula of line when scale is logarithmic

5

I would like to find y in log scale, not log(y)

6

If, for example, ln(y) = 3, y = e^3

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7

See Knowledge Base:

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8

Here's another way to do it, with a little help from AI to supplement my rusty math skills:

Plot( C, "Close", colorDefault, styleNoTitle | GetPriceStyle() ); 

bi = BarIndex();
llb = bi - LowestBars(Low);
hhb = bi - HighestBars(High);
ll = Lowest(Low);
hh = Highest(High);

logHH = log(LastValue(hh));
logLL = log(LastValue(ll));
m = (logHH - logLL) / (LastValue(hhb) - LastValue(llb));
x = bi;
b = logLL - m * LastValue(llb);
yPrime = m * x + b;
y = exp(yPrime);

Plot(y, "y", colorRed);
3 Likes
9

Thank you all !!!!

1 Like