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## How to plot a graph that has two x-axis?

Asked by Bum

### Bum (view profile)

on 29 Dec 2012

I want to plot Extreme Value Type I,II,III distribution curve. How can I plot a graph that has two x-axis? One x-axis(main) which is 'reduced variate' is linear and the other x-axis(sub) which is 'year' is non-linear. It looks like as below.

one x-axis(main): reduced variate

`   -------------------------------------------`
`   -2    -1    0    1    2    3    4    5    6`

the other x-axis(sub): year

```                -----------------------
2    5  10  20  50  100```

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## 3 Answers

### Walter Roberson (view profile)

Answer by Walter Roberson

### Walter Roberson (view profile)

on 29 Dec 2012

In the File Exchange, you will find plotxx

Bum

### Bum (view profile)

on 31 Dec 2012

Thanks. How can I display not the original x-y gragh but only the original x-axis on the transformed x-axis? This is because through the transformed x-axis, transformed x and y relationship becomes linear but it does not give the original x-axis information which is 'year'. So I want to find out original x information 'year' on the transformed x-axis and y graph.

Walter Roberson

### Walter Roberson (view profile)

on 31 Dec 2012

Which do you consider your "main" axis, and which do you consider your "sub" axis? "Which" in the sense of which one is to be the upper axis and which one is to be the lower axis?

When you speak of "transformed", is that a log() transformation? You have already said it was non-linear, but you did not indicate whether that meant "log" ?

If the user clicks on points using the data cursor, then which values should be shown to them, the "transformed" values or the "original" values?

The (x,y) that you have available to plot: are those the already-transformed values or are they the "original" values?

Bum

### Bum (view profile)

on 31 Dec 2012

Sorry for my poor explanation. (1) The main axis(lower axis) is transformed axis and the sub axis(upper axis) is original axis. (2) The relationship between original x-axis(T) and transformed x-axis(Xt) is Xt=-ln[ln(T/(T-1)] (3) If I click on points, is it possible to show both transformed and original values? If it's impossible it is okay to show the transformed values. (4) The (x,y) that I want to plot is transformed values.

Answer by Scott

### Scott (view profile)

on 31 Dec 2012

You have to be a little creative. I would start with the explanation at http://www.mathworks.com/help/matlab/creating_plots/using-multiple-x-and-y-axes.html. This isn't quite your case, but it explains how to do the overlays. You would plot the function twice on the two different axes. Then on the second one, you would need to use the 'XTick' and 'XTickLabel' properties to display the second axis as you described.

### Malcolm Lidierth (view profile)

Answer by Malcolm Lidierth

### Malcolm Lidierth (view profile)

on 31 Dec 2012

With Waterloo graphics, you can have any number of layered graphs each with independent axes (linear, log etc):

For MATLAB examples see:

http://undocumentedmatlab.com/blog/waterloo-graphics-examples/

For the project website see:

http://waterloo.sourceforge.net

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