Histogram autoscaling function?

[FlyingHyrax]

Hello again, still working on this.

I want to add an autoscaling option for the histogram. It occurred to me to check Rainmeter's source and try to see how it handles autoscaling.

I found this (https://github.com/rainmeter/rainmeter/blob/master/Library/MeterHistogram.cpp line 357)

Code: Select all

	if (m_Autoscale)
{
// Go through all values and find the max

double newValue = 0.0;
for (int i = 0; i < maxSize; ++i)
{
newValue = max(newValue, m_PrimaryValues[i]);
}

// Scale the value up to nearest power of 2
if (newValue > DBL_MAX / 2.0)
{
m_MaxPrimaryValue = DBL_MAX;
}
else
{
m_MaxPrimaryValue = 2.0;
while (m_MaxPrimaryValue < newValue)
{
m_MaxPrimaryValue *= 2.0;
}
}

Finding the maximum value from the current set is straightforward enough; I've already got that working. But I'm not sure what's happening starting in line 368 from above... can someone with C++ chops help me understand this better? If I can see what is going on I think I can translate it over to my Lua script pretty well.

Thanks

Update
I got this working to my satisfaction. The C++ code was a bit of a red herring, though it did get me thinking along the right lines in the end. Here is my solution:

Code: Select all

if auto then
			if Values[i] == maxV then
				h = maxHeight
			else
				h  = math.ceil((Values[i]/maxV)*maxHeight)
			end
		else
			h = math.ceil(Values[i]*maxHeight)
		end

The Values table holds the relative (0.0 - 1.0, or percentage) values from my CPU measure. maxHeight is the tallest a bar in the histogram can be. h is what the 'H' key in the image meter will be set to. The entire if/else is inside an iterator that goes through all of my image meters for the histogram.

It looks to me like the first nested if/else (if Values[i] == maxV) is redundant; I don't see why I can't get rid of it and just have:

Code: Select all

if auto then
	h  = math.ceil((Values[i]/maxV)*maxHeight)
else
	h = math.ceil(Values[i]*maxHeight)
end

...but for whatever reason, if I try the above things go wonky.

[jsmorley]

This might help:

http://docs.rainmeter.net/snippets/autoscale

[smurfier]

This might help:

http://docs.rainmeter.net/snippets/autoscale

A more math centric version of the autoscale function, along with a lua centric round.

Code: Select all

function AutoScale(num, idp)
	local suffix = { 'B', 'kB', 'mB', 'gB', 'tB', 'pB', 'eB', 'zB', 'yB' }
	local scale = num == 0 and 1 or math.ceil(math.log(num)/(10*math.log(2)))
	return Round(num / 1024 ^ (scale-1), idp or 0), suffix[scale] or scale
end

function Round(num, idp)
	return tonumber(string.format('%.'..(idp or 0)..'f', num))
end