Interpolation values from a table

Question

Tomás Costa 2019-9-9

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评论： Andrea 2024-12-5

Hi guys, i wonder if anyone can help me! Im trying to intepolate values from a table that i load on to matlab but i dont understand what is the thing that i am doing wrong, can someone help me? Here is my code:

I didnt put the whole code on here because i dont think it is necessary! Basically i got the areatemp1 file with has values for areas mach and temperatures and i want to interpolate to get a mach value after calculating a Area value. if anyone could help me, it would be great

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Tomás Costa 2019-9-9

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you are right, here it is:

tic
clear all 
clc
file = 'areatemp1';
file1 = 'machtemp1';
opts = detectImportOptions(file,'NumHeaderLines',0);
opts1 = detectImportOptions(file1,'NumHeaderLines',0);
T = readtable(file,opts);
T.Properties.VariableNames = {'Area','Mach','Temp'};
t = readtable(file1,opts1);
t.Properties.VariableNames = {'mach','temp'};
%condições iniciais do problema
P0 = 18:25;
T0 = 25:50;
Tc = 50:121;
D0 = input ('What is the size of the hole in microns? ');
D0 = D0*10^-6;
A0 = ((pi*D0)^2)/4;
i = 0;
j = 0;
k = 0;
Patm = 1;
R = 8.314;
A01 = (1/5)*A0;
gama = 1.4;
for i = 1:length(P0);
    P011(i) = 0.666*P0(i) + 0.333*Patm;
   for j = 1:length(T0);
       
            mass(i,j) = (0.6856*P011(i)*A01)/(R*T0(j))^(1/2);
            
            rho0(i,j) = 0.9805 * (P011(i)/(R*T0(j)));
            
            V0(i,j) = mass(j)/(rho0(j)*A0);
            
            P01(i,j) = P0(i)-(rho0(j)*V0(j)^2);
            
            T1(j) = T0(j) * 0.8316;
            V1(j) = (gama*R*T1(j))^(1/2);
            P1(j) = P01(i,j) * 0.5274;
            
        for k = 1:length(Tc);
            rhoe(k) = Patm/(R*Tc(k));
            
            
            Areas(i,j,k) = 1/((((R*T0(j))^(1/2))*rhoe(k)*V1(j))/(1.3712*P01(i,j))+sqrt((((R*T0(j))^(1/2)*rhoe(k)*V1(j))/(1.3712*P01(i,j)))^2+(R*T0(j)*rhoe(k)*(P1(j)-Patm))/(0.6856*P01(i,j))^2));
            %interpolaton
            dif = Areas(i,j,k);  %obtained however you want. Can be an array of temperatures
            machs = interp1(T.Area, T.Mach, dif);  %array of viscosities the same size as temperature
            temps = interp1(T.Area, T.Temp, dif);
            t1(j) = temps*T0(j);
            temperatura = interp1(t.mach, t.temp, machs);
            T2(j) = tempereratura*t1(j);
            if T2(j)==Tc(k)
                T2(j)=T2;
            else
                T2={};
            end
        end
              
   end   
end
   
toc
            

Dheeraj Singh 2019-9-12

Please check the variable type of T.Area . You can print the variable to see if it is of expected type or not. You can refer to the documentation of interp1 to see the expected type of T.Area.

Hope this helps.

Tomás Costa 2019-9-12

在 MATLAB Online 中打开

T.Area is a cell array of 31x1. Basically i have a table called 'areatemp1' which has values of area, mach number and temperatures. What im calculating is an area and i want to use that calculated area to interpolate on the table and export the values for mach number and temperature. I can do everything but once i get to the interpolation this error comes up:

    Error using interp1>reshapeAndSortXandV (line 414)
    X must be a vector of type double or single.
    
    Error in interp1 (line 93)
    [X,V,orig_size_v] = reshapeAndSortXandV(varargin{1},varargin{2});
    
    Error in Tese (line 51)
            machs = interp1(T.Area, T.Mach, dif);  %array of viscosities the same size as temperature

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Answer 1

Jon 2019-9-12

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https://ww2.mathworks.cn/matlabcentral/answers/479594-interpolation-values-from-a-table#answer_391598

编辑：Jon 2019-9-12

在 MATLAB Online 中打开

If T.area is a cell array, and maybe T.Mach is also a cell array you must first turn them into ordinary MATLAB vectors, (n by 1 or 1 by n arrays) before interpolating. So, for example you could do something like

area = cell2mat(T.Area)
Mach = cell2mat(T.mach)
machs = interp1(area,mach,dif);

or perhaps more compactly

machs = interp1(cell2mat(T.area),cell2mat(T.mach),dif)

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Jon 2019-9-16

编辑：Jon 2019-9-16

在 MATLAB Online 中打开

It seems that somehow your arguments aren't really what you think they are.

interp1 expects three input arguments, and looking at the code superficially, it looks like you are supplying it with 3 input arguments, so it is not obvious what the error is. Somehow, one of the three arguments you are supplying must not be evaluating to just a vector. I would suggest stepping through the code with the debugger and checking to see what those arguments evaluate to just before the function is called. Put a breakpoint on the line that generates the error. See https://www.mathworks.com/help/matlab/matlab_prog/debugging-process-and-features.html and then look in the workspace window to see what T.Area, T.Mach, and dif really are at that point. If those are as expected, e.g. cell array 31 by 1 as for T.Area, then type on the command line cell2mat(T.Area) and see what that returns (should return a vector), repeat for cell2mat(T.Mach), and then just type dif to see what that gives. Hopefully you can figure out which of those arguments is somehow not a vector and fix it from there.

If you don't want to use the debugger (although it really is the best way to debug things) you can insert the lines to just before the call to interp1 that throws the error, as earlier suggested by @Dheeraj. Note no semicolon so output will print to you command window.

T.Area
T.Mach
diff
cell2mat(T.Area)
cell2mat(T.Mach)

Jon 2019-9-17

Did this answer your question? In the end what was causing the wrong number of arguments error?

Andrea 2024-12-5

I can't speak for Tomas, but Jon your answer helped a lot! Thank you.

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Interpolation values from a table

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Interpolation values from a table

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