How to create 3D grid from data without interpolation?

Hey,

is there some function like griddata which doesnt interpolate the z data? I need some function to save all z values or the mean in the specific x,y segment.

Thanks for you help!

[José-Luis]

If you don't interpolate, then how do you get the data? Taking the mean is pretty much a linear interpolation, if I understood what you meant correctly.

[wkm42]

I have x,y,z datapoints and would like to sort them in x,y segments. So the function i'm looking for could save all the z datapoints in the x,y segments or just their mean value.

[wkm42]

For example:

Datapoints:
x: torque = [12,13,20,30]
y: speed = [512,800,1300,1506]
z: z = [2,2,1,4]

Intervalls of my desired grid:
torque_intervall = [10,20,30]
speed_intervall = [500,1000,1500,2000]

The function im looking for:

output = gridfunc(torque,speed,z,torque_intervall,speed_intervall)

output(torque=10..20,speed=500..1000)= [z(1),z(2)]
or
output(torque=10..20,speed=500..1000)= mean([z(1),z(2)])

[José-Luis]

Sorry, I don't get it.

How do you define your brackets?

What is the result you expect? Why [2,2]?

[wkm42]

I edited my example above and hope its reasonable now ;)

Your suggestion 'linear interpolation' is kinda what I'm looking for, but still griddata interpolates outside of the datapoints and misses some of the datapoints inside the grid..

[José-Luis]

That still looks like interpolation to me. It looks like you might want to find the nearest neighbor.

[wkm42]

Still 'griddata' interpolates when there are no datapoints, but doesn't when there are..

[José-Luis]

Then don't use griddata().

interp2() might provide what you need.

Did you actually look at the nearest neighbor solution I previously suggested?

[wkm42]

Yes, but nearest neighbor doesnt seem to be a solution..

interp2(): If X and Y are grid vectors, then V must be a matrix containing length(Y) rows and length(X) columns.

I just got z as a vector

[José-Luis]

I'm sorry: I don't quite get what you are after. Maybe try the 'nearest' option for griddata()?

Answer 1

[Radu Trimbitas]

interp2() has options for cubic or spline