Duration curve in matlab

Hi there

I would like to plot duration curves of discharge data with the y-axis as a "probability axis". This apparently simple job seems impossible for me to solve though.. I would like it to look like this: http://www.mekhlin.com/rasmus/varighedskurve.jpg (the dashed line is the duration curve).

An example of my data can be found here: http://www.mekhlin.com/rasmus/Q103.txt

The values are in mm/day which is also the unit I would like on the x-axis.

Thank you!

-Rasmus

Answer 1

[Ashish Uthama]

Rasmus, more clarification would help people not familiar with these curves to try and answer you. I understand the x-axis to span the range of the data (min(data) to max(data)), and at each point on this axis you want a probability of occurrence of that value to be plotted along the Y axis? (a histogram perhaps? http://www.mathworks.com/help/techdoc/ref/hist.html)

[Rasmus Petersen]

Hi Ashish. Thank you for answering. :-)

Basically I need to sort the data values form highest to lowest and then plot them versus the probability of their occurrence, p = i/(N+1). I have no problem creating these two vectors. The problem is to get that "probability axis" on the y-axis.

[Ashish Uthama]

Rasmus, sorry, I am still puzzled. I cant make much sense of the linked plot. Hard to say which 'dashed line' you are referring to.

Could you say more on what you mean by a 'probability axis'? I assume you tried plot(sortedData,p) and that did not give what you want?