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  normal probability plot
Posted by Hank on Jan-18-2014 09:01
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Hi,
I am using the chartdirector to make weibull plot. However, I encounter two problems:1. I
want to use the y-axis scale which like normal probability plot(like the attachment). How
can I get it? 2.Does it possible use the default 2D scatter symbols without the symbol
frame?
Thanks.
i11normalplot.jpg

  Re: normal probability plot
Posted by Peter Kwan on Jan-21-2014 01:06
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Hi Hank,

For your case, the y-coordinate is the z statistic from -3.08 to 3.08. However, instead of
putting the labels from -3 to 3 on the y-axis, some people like to label the y-axis using
cumulative distribution. You may use the standard normal distribution table to convert
between the z statistic and its cumulative distribution. See:

http://www.mathsisfun.com/data/standard-normal-distribution-table.html

So for configuring the y-axis, the code is like (in Java):

//y-axis scale is -3 to 3
c.yAxis().setLinearScale2(-3.08, 3.08, new String[] {});

//The labels you want to be put on the y-axis and their z statistics from the normal
distribution table
String[] labels = {"0.01", "1", "5", "10", ........ };
double[] labelZ = {-3.08, -2.33, -1.645, -1.28, ... };

for (int i = 0; i < labels.length; ++i)
    c.yAxis().addLabel(labelZ[i], labels[i]);

For the symbols, you can use a scatter layer. You may specify the symbol fill color and
edge color in addScatterLayer. You can use the same color for the fill color and edge
color, in which case, the symbol will not have any frame.

Hope this can help.

Regards
Peter Kwan