How to find a value from column 1 for given column 2 and 3 values.

Hi there, new to Matlab and have a small task which I need help with.

I have three columns, first shows velocity, second shows x-coordinates and third shows y-coordinates. I want to be able to find the velocities for given x,y coordinates. I have about 36,000 values for each so basically need an efficient way to do this. Thanks in advance.

[madhan ravi]

use for loop

[madhan ravi]

can you upload the datas as a file by clicking the paper clip button.

[Yahya Khan]

I need to be able to create a control volume, so basically a square that has velocity for each point along the boundary. The csv file has u-velocity, v-velocity, x-coordinate, y-coordinate and z-coordinate. I can basically ignore the z-coordinates and work with u an v velocities separately.

Answer 1

[Matt J]

Use griddedInterpolant

F=griddedInteprolant({x,y},velocity);

[Yahya Khan]

I've tried using griddedinterpolation but keep on getting errors such as 'grid vectors must be strictly monotonically increasing' What format do I need to have the data in? Also is it possible to create a matrix of velocity from the x,y coordinates as that would make it the most useful to work with?

[Matt J]

There are several options for that which are explained in the griddedInterpolant documentation, but in this example, I intended x and y to be grid vectors.

Yes, you should give the velocity data to griddedInterpolant in matrix form, using reshape() appropriatately. If the velocity data is not sampled from a regular grid, you should probably be using scatteredInterpolant() instead.

Answer 2

[ahmed nebli]

u can use a code like this

% A is you matrix for i=1:size(A,1) y(i)=A(i,1); %the volocity for each x , y end

[Image Analyst]

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