How to interpolate ‘z’ for one value of ‘x’ but multiple values of y?

Question

JD 2019-10-2

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/483248-how-to-interpolate-z-for-one-value-of-x-but-multiple-values-of-y

评论： JD 2019-10-3

采纳的回答： Matt J

I have an array x of size 1x56 An array y of size 1x20 And an array z of size (20x56)

I want to interpolate to find ‘z’ for a specific value of x but multiple y.

I am trying to plot Interp2(x,y,z,1400,y)

Z =f(x,y,z)

But it doesn’t seem to be working right. Anyone have any ideas?

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JD 2019-10-2

编辑：JD 2019-10-2

在 MATLAB Online 中打开

ICE.map_w = [850:100:6400]*2*pi/60; ICE.map_T = [10:10:200]';
ICE_m_f_dot_map_temp_w = [850*ones(1,5) 1400*ones(1,12) 1900*ones(1,13)... 
        2500*ones(1,13) 3000*ones(1,14) 3600*ones(1,14) 4200*ones(1,14)... 
        4700*ones(1,14) 5300*ones(1,14) 5800*ones(1,14) 6400*ones(1,13)]*2*pi/60;
%2.134 2.372 2.563 2.943... 0.022 0.620 0.799 1.019 1.267 1.540 1.817 2.084 2.354 2.628 2.905 3.155 3.519 4.031... 0.028 0.782 0.996 1.249 1.546 1.866 2.189 2.513 2.841 3.169 3.459 3.758 4.175 4.763... 0.034 0.967 1.220 1.513 1.860 2.230 2.597 2.970 3.351 3.732 4.055 4.412 5.039 6.133... 0.042 1.184 1.474 1.804 2.199 2.623 3.039 3.455 3.905 4.341 4.749 5.229 6.035 7.247... 0.054 1.463 1.757 2.108 2.547 3.033 3.518 4.017 4.567 5.125 5.670 6.298 7.207 8.345... 0.069 1.795 2.061 2.417 2.897 3.450 4.027 4.648 5.336 6.076 6.788 7.563 8.609 9.876... 0.084 2.129 2.379 2.739 3.246 3.862 4.545 5.301 6.146 7.045 7.943 8.934 10.209]./1000;
% engine torque [Nm]
ICE_m_f_dot_map_temp_T = [0.00	4.74	19.22	33.71	48.19...
0.00	4.74	19.22	33.71	48.19	62.67	77.15	91.64	106.12	120.60	135.08	149.57...
0.00	4.74	19.22	33.71	48.19	62.67	77.15	91.64	106.12	120.60	135.08	149.57	164.05...
0.00	4.74	19.22	33.71	48.19	62.67	77.15	91.64	106.12	120.60	135.08	149.57	164.05...
0.00	4.74	19.22	33.71	48.19	62.67	77.15	91.64	106.12	120.60	135.08	149.57	164.05 178.53...
0.00	4.74	19.22	33.71	48.19	62.67	77.15	91.64	106.12	120.60	135.08	149.57	164.05	178.53...
0.00	4.74	19.22	33.71	48.19	62.67	77.15	91.64	106.12	120.60	135.08	149.57	164.05	178.53...
0.00	4.74	19.22	33.71	48.19	62.67	77.15	91.64	106.12	120.60	135.08	149.57	164.05	178.53...
0.00	4.74	19.22	33.71	48.19	62.67	77.15	91.64	106.12	120.60	135.08	149.57	164.05	178.53...
0.00	4.74	19.22	33.71	48.19	62.67	77.15	91.64	106.12	120.60	135.08	149.57	164.05	178.53...
0.00	4.74	19.22	33.71	48.19	62.67	77.15	91.64	106.12	120.60	135.08	149.57	164.05
]; 
% fuel rate [kg/s]
ICE_m_f_dot_map_temp = [0.000	0.082	0.133	0.185	0.228...
 0.000	0.240	0.335	0.443	0.556	0.681	0.811	0.937	1.069	1.210	1.346	1.536...
 0.012	0.349	0.474	0.618	0.775	0.956	1.137	1.305	1.478	1.666	1.851	2.029	2.399...
 0.016	0.475	0.630	0.820	1.021	1.247	1.479	1.692	1.907	2.134	2.372	2.563	2.943...
 0.022	0.620	0.799	1.019	1.267	1.540	1.817	2.084	2.354	2.628	2.905	3.155	3.519	4.031...
 0.028	0.782	0.996	1.249	1.546	1.866	2.189	2.513	2.841	3.169	3.459	3.758	4.175	4.763...
 0.034	0.967	1.220	1.513	1.860	2.230	2.597	2.970	3.351	3.732	4.055	4.412	5.039	6.133...
 0.042	1.184	1.474	1.804	2.199	2.623	3.039	3.455	3.905	4.341	4.749	5.229	6.035	7.247...
 0.054	1.463	1.757	2.108	2.547	3.033	3.518	4.017	4.567	5.125	5.670	6.298	7.207	8.345...
 0.069	1.795	2.061	2.417	2.897	3.450	4.027	4.648	5.336	6.076	6.788	7.563	8.609	9.876...
 0.084	2.129	2.379	2.739	3.246	3.862	4.545	5.301	6.146	7.045	7.943	8.934	10.209]./1000; 
% speed and torque lists for the griddata 
ICE.map_w = [850:100:6400]*2*pi/60;
ICE.map_T = [10:10:200]'; 
ICE.map_m_dot = griddata(ICE_m_f_dot_map_temp_w, ICE_m_f_dot_map_temp_T, ICE_m_f_dot_map_temp, ICE.map_w, ICE.map_T)';
pma = (ICE.map_m_dot'*4*pi*43.5*10e6)./(ICE.map_w.*2e-3);
mfdot_6400c = (pma.*ICE.map_w*2e-3)/(4*pi*43.5*10e6); mfdot_6400 = interp2(ICE.map_w,ICE.map_T,mfdot_6400c',6400*2*pi/60,ICE.map_T); pma_6400 = (mfdot_6400'*4*pi*43.5*10e6)./((6400*2*pi/(60))*2e-3)

The pma_6400 gives me NaN

Walter Roberson 2019-10-2

在 MATLAB Online 中打开

Error using griddedInterpolant
The grid vectors do not define a grid of points that match the given values.

That is reported inside interp2(). The fix for that is to change

mfdot_6400 = interp2(ICE.map_w,ICE.map_T,mfdot_6400c',6400*2*pi/60,ICE.map_T);

to

mfdot_6400 = interp2(ICE.map_w,ICE.map_T,mfdot_6400c,6400*2*pi/60,ICE.map_T);

That is, remove the complex conjugate transpose.

However you will still get NaN. And that is because:

>> max(ICE.map_w)
ans =
           664.97044500984
>> 6400*2*pi/60
ans =
          670.206432765823

Your probe x is outside the range of any of the data you define.

JD 2019-10-3

That makes sense, thank you both for the help!

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Answer 1

Matt J 2019-10-2

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/483248-how-to-interpolate-z-for-one-value-of-x-but-multiple-values-of-y#answer_394529

If an interpolation result is giving you NaN, it normally means you are interpolating at a location which is outside the area covered by your points - hence there is no data there to interpolate between.