Unable to perform assignment because the indices on the left side are not compatible with the size of the right side.

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Christopher Redard 2021-11-23

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https://ww2.mathworks.cn/matlabcentral/answers/1593349-unable-to-perform-assignment-because-the-indices-on-the-left-side-are-not-compatible-with-the-size-o

评论： Peter Perkins 2021-11-23

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Code Below are two separate functions both returning the following error:

Unable to perform assignment because the indices on the left side are not compatible with the size of the right side.

Function One:

clear all;
close all;
clc;
T_table = xlsread('air_data_v2','A2','A5:A125');
u_table = xlsread('air_data_v2','A2','B5:B125');
s_table = xlsread('air_data_v2','A2','D5:D125');
h_table = xlsread('air_data_v2','A2','C5:C125');
PR = [1 2 3];
Tmax = [1000 1200 1400];
for i = 1:length(PR)
    [KenergyC(i),Nc(i)] = Project2AFunctions1(PR,Tmax);
end
function [KenergyC,Nc] = Project2AFunctions1(PR,Tmax)
R = .287;
Cp = 1.004;
Cv = .7241;
k = Cp/Cv;
%initial state
P1 = 23800; %Pa
T1 = 220; %-54C at 35000 feet in the sky
v1 = R*T1/P1;
%Tmax = 1000;
P2 = P1*3; %Pressure Ratio
Pcompressor = P1:1e3:P2;
for i = 1:length(Pcompressor)
    scompressor(i) = xlsread('air_data_v2','A2','D7');
    Tcompressor(i) = sqrt(Pcompressor(i));
    vcompressor(i) = R*Tcompressor(i)/Pcompressor(i);
end
hcompressor = Cp*(Tcompressor(end)-T1);
%Combustor (State 2)
Tcombustor = 266.08:Tmax(end);
for j = 1:length(Tcombustor)
    Pcombustor(j) = Pcompressor(end);
    vcombustor(j) = R.*Tcombustor(j)/Pcombustor(j);
    scombustor(j) = scompressor(end) + Cp.*log(Tcombustor(j)/Tcombustor(1));
end
hcombustor = Cp*(Tmax(end)-Tcompressor(end));
%Turbine (State 3)
Pturbine = P2:-1e3:P1;
for l = 1:length(Pturbine)
    Tturbine(l) = Tcombustor(end).*10.^((R/Cp)*log(Pturbine(l)/P2));
    vturbine(l) = ((70800.*vcombustor(end).^k)/(Pturbine(l))).^(1/k);
    sturbine(l) = scombustor(end);
end
hturbine = Cp*(999.08-Tcombustor(end));
%Outlet of system (State 4)
Texit = Tcompressor(1):Tturbine(end)+91.779;
for m = 1:length(Texit)
    sexit(m) = scompressor(end) + Cp.*log(Texit(m)/Texit(1));
end
Pexit = [Pturbine(end) Pturbine(end)];
vexit = [vcompressor(1) vturbine(end)];
hexit = Cp*(Texit(end)-Tturbine(end));
S3 = sturbine(end);
%5
P5 = P1;
S5 = S3;
V5 = ((Pturbine.*vturbine.^k)/P5).^(1/k);
T5 = (P5.*V5)/R;
h5c = Cp*(T5-Tturbine(end));
%constant CP
KenergyC = h5c-hexit;
Nc = 1-PR.^(-R/Cp);
end

Function two:

clear all;
close all;
clc;
PR = [1 2 3];
Tmax = [1000 1200 1400];
for i = 1:length(PR)
    [KenergyNC(i),Nnc(i)] = Project2AFunctions2(PR,Tmax);
end
function [KenergyNC,Nnc] = Project2AFunctions2(PR,Tmax)
R = .287;
Cp = 1.004;
Cv = .7241;
k = Cp/Cv;
T_table = xlsread('air_data_v2','A2','A5:A125');
u_table = xlsread('air_data_v2','A2','B5:B125');
s_table = xlsread('air_data_v2','A2','D5:D125');
h_table = xlsread('air_data_v2','A2','C5:C125');
%non constant
%State 1
p1 = 23800;
t1 = 220;
v1 = R*t1/p1;
s1 = interp1(T_table,s_table,t1);
h1 = interp1(T_table,h_table,t1);
sT1 = interp1(h_table,s_table,h1);
%State 2
s2 = s1;
p2 = p1*PR;
sT2 = sT1 + R*log(p2/p1);
t2 = interp1(s_table,T_table,sT2);
v2 = R*t2/71400;
h2 = interp1(T_table,h_table,t2);
%State 3
p3 = p2;
sT3 = interp1(T_table,s_table,Tmax);
s3 = sT3-sT2 - (R*log(p3/p2))+s2;
v3 = R*Tmax/p3;
h3 = interp1(T_table,h_table,Tmax);
%State 4
h4 = h3+h1-h2;
s4 = s3;
sT4 = interp1(h_table,s_table,h4);
t4 = interp1(h_table,T_table,h4);
p4 = (exp(sT4-sT3)/R).*p3;
v4 = R*t4/p4;
%State 5
s5 = s4;
p5 = p1;
sT5 = sT3+(R*log(p5/p3(1)));
t5 = interp1(s_table,T_table,sT5);
h5 = interp1(T_table,h_table,t5);
v5 = R*t5/p5;
%NonConstant CP
KenergyNC = h5-h4;
Nnc = (h5-h4)/(h3-h2);
end

I would really appreciate knowing what is causing it. Thanks

2 个评论
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per isakson 2021-11-23

See TUTORIAL: how to ask a question (on Answers) and get a fast answer

We cannot run your code, since we don't have the Excel files. You may not expect us to spot the cause of the error by inspection of the code. You should at least provide the full error message.

Peter Perkins 2021-11-23

I really, strongly recommend that you use readtable, or readmatrix, instead of xlsread.

Beyond that set a breakpoint at the line the error is coming from, and figure out what's the wrong size, and work your way backwards to figure out why.

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Answer 1

KSSV 2021-11-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1593349-unable-to-perform-assignment-because-the-indices-on-the-left-side-are-not-compatible-with-the-size-o#answer_837959

在 MATLAB Online 中打开

The error is clear, you are trying to save more number of elements on the LHS then it is intialized for.

Example:

A = zeros(3,3) ;  % A should have 3x3 numbers 
A(1,:) = rand(1,3) ;  % no error, you are saving three elements as it is innitliazed 
A(2,:) = rand(1,4)   % error, becuase you are trying to save four number instead of 3 
Unable to perform assignment because the size of the left side is 1-by-3 and the size of the right side is 1-by-4.