Reputation: 2043
I have a problem with setting the maximum and minimum values for the y-axis of my mschart. When setting the max or min to a value, say 10.025, the value the chart sets as max is 10.024999618530273.
mainChart.ChartAreas[selectedChartArea].AxisY.Maximum = GetRoundYAxisMax(newYMax, newYRange);
mainChart.ChartAreas[selectedChartArea].AxisY.Minimum = GetRoundYAxisMin(newYMin, newYRange);
The GetRoundYAxisMax method just returns a "round" value. Code below.
private float GetRoundYAxisMax(double calculatedMax, double yAxisRange)
{
double rangeFactor = 0;
if (yAxisRange > 10)
rangeFactor = 1;
else if (yAxisRange > 1)
rangeFactor = 4;
else if (yAxisRange > 0.1)
rangeFactor = 40;
else if (yAxisRange > 0.01)
rangeFactor = 400;
else if (yAxisRange > 0.001)
rangeFactor = 4000;
else if (yAxisRange > 0.0001)
rangeFactor = 40000;
else
rangeFactor = 400000;
float returnValue = (float)(Math.Round(calculatedMax * rangeFactor, MidpointRounding.ToEven) / rangeFactor);
return returnValue;
}
The rounding code evaluates properly and returns a correctly rounded value, but when setting this value to the max or min value on the y-axis it sets a value very close to it, but not rounded.
Any ideas why this is happening?
Upvotes: 0
Views: 2529
Reputation: 1
Just answering why 10.024999618530273 rather than 10.025. Nothing on a computer is infinite in precision. You have ( IIRC ) 80 bits to represent your number. Part is exponent part is mantissa. What is happening is that 10.025 is not a number that has perfect representation in that number of bits. You dont get the whole number line, you get integral marks along it. ( take a random 80 bit double. That is a point on the number line. Now, add the smallest increment to that 80 bit double that is possible. Another point on the line. Now, in the "real" ( pun intended ) world, there are an infinite number of real points. Any point on the line you try to represent on a real world number line will be represented as one of the two points that bound that point in the 80 bit world ).
Upvotes: 0
Reputation: 2043
You can set the axis label style to round the un-rounded values:
mainChart.ChartAreas[selectedChartArea].AxisY.LabelStyle.Format = "#.###";
Upvotes: 1