Data Reduction and sub set of data

Hello every body,

I'm new with Matlab. I want to write a code whcih can be used on my grid file to reduce it to region of my interest. I have lat lon and displacement values. I want to define a circle of radius 100Km from a central point(lat lon) so that everything outside the circle delete and I get a resultant grid file with data of my own interest.

I would like to pay some reward (as Im a student) for this work.

Please let me know if anybody is interested

Thanks

Answer 1

[Image Analyst]

Save some money and see the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F

[amberly hadden]

Thanks image analyst

but this is for image I have a very large grid file which is giving me error when I do meshgrid (out of memory)

[Image Analyst]

How big is it? How many points across and vertically do you have? What does your displacement data look like. Please read this

[amberly hadden]

I'm sorry I dont what to do and how to ask as I'm stressed.

My data file is having 3 columns and 3070250 rows (lat,lo,displacement).

Thanks for guidence

[Image Analyst]

What does displacement have to do with anything? Just read in the file, compute distances and keep those that are closer than 100. Something like

m = importdata(filename);
x = m(:, 1);
y = m(:, 2);
% Define reference point.  Could be whatever you want.
xRef = x(1);
yRef = y(1);
% Find distances of every point from the ref point
distances = sqrt((x-xRef).^2+(y-yRef).^2);
% Find rows closer than 100
indexesOfClosePoints = distances < 100;
% Extract only those
closePoints = m(indexesOfClosePoints, :);

[amberly hadden]

Thank you very very much. I'ill try this it looks very reasonable.

Thanks again

[amberly hadden]

Hi Image analyst

Could you please guide me how can I find the location of a point lets say lat lon z, I want maximum z which will be max(A(:,3)) now I want to locate its position and then want to get values of (lat and lon) at max z. In next step I want to reffer these values as as xRef and Yref

Thanks in advance :)

[Image Analyst]

[maxZ, indexOfMaxZ] = max(z);
xRef = x(indexOfMaxZ);
yRef = y(indexOfMaxZ);

[amberly hadden]

great thanks very much

[amberly hadden]

Dear image anlyst

I was trying to write a small code in which I just want to select part of data. lets say attached file. I just want to select region between

58.4818969729 26.9251161301 1.6595774889 and 58.497736653 26.9251161301 1.1188951731

can anybody help me in this regard

Thanks in advance Amberly

[Image Analyst]

I don't see any attached file. Did you forget to click the "Attach file" button after you browsed to it?

If it's a follow up question, attach it above by editing your question. If it's totally unrelated to this question, then post a new question.

[amberly hadden]

Sorry I did uploaded and yes your are right :) forget to click attached. I did posted a new question but didt get any response you can browse title of it Sampling data from a large data file Thanks

[amberly hadden]

Hey! can you see file now

[Image Analyst]

Try this code:

numbers = xlsread('test.xls');
lats = numbers(:, 1);
lons = numbers(:, 2);
z = numbers(:, 3);
lat1 = 58.4
lon1 = 26.1
z1 = 1.65
lat2 = 58.5
lon2 = 27
z2 = 1.11
desiredLats = lats >= lat1 & lats <= lat2
desiredLons = lons > lon1 & lons <= lon2
desiredZs = z <= z1  & z >= z2
rowsToExtract = desiredLats & desiredLons & desiredZs
extractedRows = numbers(rowsToExtract, :)

[amberly hadden]

hi its producing same data set insread

solved my problem

:) Thanks