How to calculate a median value of each interval?

Hi everyone,

I want to make a line plot and for that purpose I need to calculate the median value of each interval. In my data Y (8767x1 double) is temperature and X (8767x1 double) is phase so I need to calculate the phase median value of each temperature interval such as 1 degree. And then plot it. Any suggestions how it can be done? Thank you.

Please find the attached data.

[Rik]

If you can't solve your entire problem, try splitting it up in steps.

Can you load the data to a Matlab variable?

Do you know how to select parts of your array?

Do you know how to calculate the median?

There is a shortcut with accumarray, but that is a later concern.

[Mathieu NOE]

I am not sure to understand your request and also your data array if full on NaN's either on variable or the other one ... how are we supposed to make the correlation between temperature vs phase or vice versa if one data is always NaN ??

[Zhou Ci]

@Mathieu NOE I want to plot this data where X should be on X-axis and Y (temp) on Y-axis. For plotting purpose, I need to calculate the phase (X) median value of each temperature (Y) interval such as 1 degree. NaN values can be omitted/deleted from these 2 column vectors.

[Zhou Ci]

@Rik 1) I used MATLAB to get these column vectors. Just for the sake of convinence I copied data to excel and attached here.

2) Do you mean selecting just the values and deleting NaN? I actually deleted all the NaN from X and respective values from Y column but still didn't get desired results.

3) Regarding median, I am facing problem in plotting because I need to calculate the phase (X) median value of each temperature (Y) interval and then plot it.

[Rik]

I meant selecting specific values from a vector. If you find out which positions round to the same degree, you can use that to calculate the median of only those values. If you do that in a loop, you will have found all relevant medians.

[Zhou Ci]

@Rik Sir, Can you please elaborate this line?

'If you find out which positions round to the same degree, you can use that to calculate the median of only those values'.

Secondly, how can it be done using loop?

Answer 1

[Rik]

%generate some random data
temperature=15+10*rand(8767,1);
phase=360*rand(size(temperature));

temperature_rounded=round(temperature,0);

T=unique(temperature_rounded);
P=NaN(size(T));
for n=1:numel(T)
    L= T==T(n); %select all positions where the rounded temperature is a specific value
    P(n)=median(phase(L));%calculate the median for this selection
end
plot(T,P)