Incorrect use of '=' operator. To assign a value to a variable, use '='. To compare values for equality, use '=='.

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asd ad 2020-8-14

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https://ww2.mathworks.cn/matlabcentral/answers/579525-incorrect-use-of-operator-to-assign-a-value-to-a-variable-use-to-compare-values-for-equal

评论： Steven Lord 2022-10-5

Hello everyone,

I'm getting the aformentioned error for the RL2 variable but I do not want to compare values for equality. I just want to put RL2 = RL/2. This problem persists even when I remove that line of code. The same problem occurs for H matrix when I remove the line of code for RL2 and the same occurs for R when I remove the line of code for H matrix. Why is this happening?

Thanks

clear all
close all
clc
R1 = 0; R2 = 100; R3 = 125; R4 = 150; R5 = 200; R6 = 250; R7 = 500; R8 = 1000;
R9 = 2000;
L1 = 0; L2 = 2.5; L3 = 5; L4 = 7.5; L5 = 10; L6 = 12.5; L7 = 15; L8 = 17.5; L9 = 20; 
RL = [R1*L1 R2*L1 R3*L1 R4*L1 R5*L1 R6*L1 R7*L1 R8*L1 R9*L1;
    R1*L2 R2*L2 R3*L2 R4*L2 R5*L2 R6*L2 R7*L2 R8*L2 R9*L2;
    R1*L3 R2*L3 R3*L3 R4*L3 R5*L3 R6*L3 R7*L3 R8*L3 R9*L3;
    R1*L4 R2*L4 R3*L4 R4*L4 R5*L4 R6*L4 R7*L4 R8*L4 R9*L4;
    R1*L5 R2*L5 R3*L5 R4*L5 R5*L5 R6*L5 R7*L5 R8*L5 R9*L5;
    R1*L6 R2*L6 R3*L6 R4*L6 R5*L6 R6*L6 R7*L6 R8*L6 R9*L6;
    R1*L7 R2*L7 R3*L7 R4*L7 R5*L7 R6*L7 R7*L7 R8*L7 R9*L7;
    R1*L8 R2*L8 R3*L8 R4*L8 R5*L8 R6*L8 R7*L8 R8*L8 R9*L8;
    R1*L9 R2*L9 R3*L9 R4*L9 R5*L9 R6*L9 R7*L9 R8*L9 R9*L9;
    
RL2 = (RL/2);
H = [73.00 73.00 73.00 73.00 73.00 73.00 73.00 73.00 73.00;
     70.17 70.17 70.17 70.17 70.17 70.17 70.17 70.17 70.17; 
     67.34 67.34 67.34 67.34 67.34 67.34 67.34 67.34 67.34; 
     64.19 64.19 64.19 64.19 64.19 64.19 64.19 64.19 64.19;
     61.36 61.36 61.36 61.36 61.36 61.36 61.36 61.36 61.36;
     58.53 58.53 58.53 58.53 58.53 58.53 58.53 58.53 58.53;
     55.38 55.38 55.38 55.38 55.38 55.38 55.38 55.38 55.38;
     49.72 49.72 49.72 49.72 49.72 49.72 49.72 49.72 49.72;
     43.74 43.74 43.74 43.74 43.74 43.74 43.74 43.74 43.74;
     37.76 37.76 37.76 37.76 37.76 37.76 37.76 37.76 37.76; 
     32.09 32.09 32.09 32.09 32.09 32.09 32.09 32.09 32.09;
     23.60 23.60 23.60 23.60 23.60 23.60 23.60 23.60 23.60;
     15.73 15.73 15.73 15.73 15.73 15.73 15.73 15.73 15.73;
     7.87  7.87 7.87 7.87 7.87 7.87 7.87 7.87 7.87;
     0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00];
 
 R = [R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9;
     R1 R2 R3 R4 R5 R6 R7 R8 R9];
 
contourf(RL2,R,H)
k = colorbar;
cmap = colormap;
ax = gca;
ax.Color = cmap(1, :);
k.Label.String = 'Relative Humidity (%)';
xlabel('Length (\mum)')
ylabel('Radius (\mum)')

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Ruslan Smirnov 2022-10-5

编辑：Ruslan Smirnov 2022-10-5

surprisingly, when trying to execute code section by section, problems with incomplete lines or wrong usage of = operator affect the execution of previous lines; pathetic

Steven Lord 2022-10-5

在 MATLAB Online 中打开

@asd ad Rather than defining individual variables named R1 through R9 and L1 through L9, I recommend defining a vector.

R = 1:9;
L = 10:19;

With vectors and implicit expansion, you can assemble those matrices with a lot less typing.

A = R.*(L.')
A = 10×9
  20    30    40    50    60    70    80    90
  22    33    44    55    66    77    88    99
  24    36    48    60    72    84    96   108
  26    39    52    65    78    91   104   117
  28    42    56    70    84    98   112   126
  30    45    60    75    90   105   120   135
  32    48    64    80    96   112   128   144
  34    51    68    85   102   119   136   153
  36    54    72    90   108   126   144   162
  38    57    76    95   114   133   152   171

As a check, A(3,4) should be R(4)*L(3).

[A(3,4) R(4)*L(3)]
ans = 1×2
    48    48

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Answer 1

Walter Roberson 2020-8-14

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在 MATLAB Online 中打开

RL2 = (RL/2;

That is an incomplete expression that would cause problems for what follows.

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asd ad 2020-8-14

Oh yes that was the problem. Thank you

Walter Roberson 2020-8-14

在 MATLAB Online 中打开

After you put in the ] for RL then there are no more syntax errors, but you have the problem that in your call

contourf(RL2,R,H)

then RL2 is 9 x 9 but R and H are 15 x 9

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Incorrect use of '=' operator. To assign a value to a variable, use '='. To compare values for equality, use '=='.

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