Interpolating scattered data within a shapefile/worldmap

2020 3 30
1 个回答
更新时间：2020 3 31
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Hi I have x,y,zi scattered data, where x is lon, y is lat and zi is the data, I want to interpolate and extrapolate the data within the land boundaries, I used
vq = griddata(x,y,zi,xi,yi);
However, the interpolation and extrapolation was not made as desired.

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BN
BN 2020-3-30
编辑：BN 2020-3-30
Use scatteredInterpolant (https://www.mathworks.com/help/matlab/ref/scatteredinterpolant.html). It is very similar to griddata but I guess it inter polate across all area that you want.
SChow
SChow 2020-3-30
I have tried using scatteredinterpolant, it does not work. Please find the attached file of scattered data.
clc
clear
[LAT LON]=cdtgrid(1.875);%%making meshgrid for desired data
obs_data=xlsread('Z:\CP_c.csv');
loni = obs_data(:,2) ;
lati = obs_data(:,1) ;
% zi = interp2(LONi,LATi,xi,loni,lati) ;
F=scatteredInterpolant(loni,lati,obs_data(:,5),'linear','linear');
F.Method = 'linear';
vq1 = F(LAT,LON);
imagesc(vq1)

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回答（1 个）

darova
darova 2020-3-30

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Here is my effort. Am i succeeded?
S = importdata('CP_c.csv');
A = S.data;
x = A(:,1);
y = A(:,2);
z = A(:,3);
xx = linspace(min(x),max(x),20);
yy = linspace(min(y),max(y),20);
[X,Y] = meshgrid(xx,yy);
Z = griddata(x,y,z,X,Y);
surf(X,Y,Z)

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SChow
SChow 2020-3-30
编辑：SChow 2020-3-30
hi darova,
With your code (slightly changes), I get fig 1, I do not get desired results (see fig 2):
clc
clear
addpath ( 'Z: \ CDT \ chadagreene-CDT-dc37894 \ cdt \' )
S = importdata ( 'Z: \ NO2_WORK \ CP_c.csv' );
A = S.data;
x = A (:, 1);
y = A (:, 2);
z = A (:, 3);
% xx = linspace (min (x), max (x), 20);
% yy = linspace (min (y), max (y), 20);
[X, Y] = cdtgrid (0.5); %%% meshgrid at 0.5 degree res
Z = griddata (x, y, z, X, Y);
imagescn (X, Y, Z)
darova
darova 2020-3-30
It's not easy task. Do you have coordinates of each separate region? (black)
SChow
SChow 2020-3-30
编辑：SChow 2020-3-30
Hi darova,
Even if we can interpolate+extrapolate to the whole extent of fig1 (including the white portion), I can clip the otputs for oceans using island
Can you help me interpolate the point data to the extent of the globe?
[LAT, LON] = cdtgrid (0.5); %%% meshgrid of X and Y for the globe at 0.5 degree res
darova
darova 2020-3-30
I tried this
worldmap([min(x) max(x)],[min(y) max(y)])
load coast
plotm(lat, long)
hold on
plotm(x,y,'.g')
hold off
Looks like you don't have enough data for color
SChow
SChow 2020-3-30
I could plot similar scatter plot with fastscatter.
I need to interpolate the data from these points to the extent of the world
darova
darova 2020-3-30
You don't have points for RUssia and Mexico
SChow
SChow 2020-3-31
Yes, that is why I want to interpolate the data to Mexico and Russia.

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2020-3-30

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