How to find the Y Value in a Array and Locate corresponding X Value

Hi,

I have series of questions regarding an array of data that i have and how to capture the value and plot and find relevant values in X axis. Below is the query.

1. I have an array of data 100x550. I need to find the 10% of 550 data and 90% of 550 data.
2. Once this is captured i should be able to locate them in the 100x550 array of data
3. Later i should be able to capture the relevant x1 & x2 values
4. Finally plot.

Below is the code upto which i was successful in capturing point 1, but stuck with 2, 3 & 4

x1 = csvread('Data1_Nm.csv');

x2 = x1(:,550);

x3 =(10/100)*x2;

x4 = (90/100)*x2;

X=0;

for i = 1:1:length(x1)

X=find(x1(i)~=x4(i));

end

Hope to get some help, any more details needed please let me know.

Thank you

Regards

Raghu

(Mechanical Engineer - Trying to Learn Matlab and Simulink)

Answer 1

[Spencer Chen]

You are on the right track. Let's start with:

  X=find(x1(i)~=x4(i));

Indexing into x1 and x4 is your problem here. Think about the difference between how you index into a 2D matrix (x1) and a 1D vector (x4).

Once you work that out, then rethink how to do this for-loop properly:

for i = 1:1:length(x1)  ...     

Lastly, you need to think about yout "X". The way you have set it up, the value in X is overwritten every iteration of the for-loop. So you will only get the last value of X out from your loop. So you'll need to think about how you can get every calculated "X" out from your for-loop.

Finally, not sure of the exact problem that you were asked to solve. I suspect that you may be misreading it. I have a suspision that your original problem may related to the function quantile().

Blessings,

Spencer