Help With Error: "Attempted to access S_0(2); index out of bounds because numel(S_0)=1."

Question

Andrew 2014-3-26

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https://ww2.mathworks.cn/matlabcentral/answers/123120-help-with-error-attempted-to-access-s_0-2-index-out-of-bounds-because-numel-s_0-1

编辑： Walter Roberson 2014-3-26

Hi, so I'm trying to get this part of the program running in matlab, and the error, "Attempted to access S_0(2); index out of bounds because numel(S_0)=1." comes up. here's what I have of the code so far. I'm pretty new to matlab, so I don't know all the functions. I'm trying to find the sum of S_0 without using the "sum" function. Please help asap I need this fast!

Here's the code:

% Inputs and Equations that Calculate the Equations for the Coefficient C_l 
f = input('Please Enter the First Digit of the NACA Number'); % Input for the Max. Camber
s = input('Please Enter the Second Digit of the NACA Number'); % Input for the Position of Max. Camber
theta = input('Please Enter Angle of Attack in Degrees'); % Angle of Attack in Degrees
M = f/100; % Calculates the Maximum Camber of the Wing
P = s/10; % Calculates the Position of the Maximum Camber of the Wing
x = .5*(1+cos(theta)); % Distance
n = 180/(theta)+1; % Calculates the Number of Rectangles to be Used for the Integral
% Calculation of dy_c/dx for Values of Different x
if x>= 0 && x<=P;
     dy_c1_dx = (M/P^2)*(2*P-2*x); % This is the Gradient if 0<=X and X<=P
  elseif x>=P && x<=1;
      dy_c2_dx = (M/(1-P)^2)*(2*P-2*x); % This is the Gradient if P<=X and X<=1
  end
S_0 = 0
S_1 = 0
for i = 1:n
      if x>=0 && x<= P;
          S_0(i) = S_0(i)+(dy_c1_dx);
          S_1(i) = S_1(i)+(dy_c1_dx)*cos(theta);
      elseif x> P && x<=1;
          S_0(i) = S_0(i)+(dy_c2_dx);
          S_1(i) = S_1(i)+(dy_c2_dx)*cos(theta);
      end
  end

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Answer 1

Chandrasekhar 2014-3-26

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/123120-help-with-error-attempted-to-access-s_0-2-index-out-of-bounds-because-numel-s_0-1#answer_130442

In the code u have declared S_0 and S_1 as scalars and you are trying to access them as vectors in the for loop.S_0 and S_1 has only one element where as you are trying to access the second element of S_0 and S_1 which doesnt exist

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Chandrasekhar 2014-3-26

在 MATLAB Online 中打开

Try the below code

% Inputs and Equations that Calculate the Equations for the Coefficient C_l

f = input('Please Enter the First Digit of the NACA Number'); % Input for the Max. Camber
s = input('Please Enter the Second Digit of the NACA Number'); % Input for the Position of Max. Camber
theta = input('Please Enter Angle of Attack in Degrees'); % Angle of Attack in Degrees
M = f/100; % Calculates the Maximum Camber of the Wing
P = s/10; % Calculates the Position of the Maximum Camber of the Wing
x = .5*(1+cos(theta)); % Distance
n = 180/(theta)+1; % Calculates the Number of Rectangles to be Used for the Integral
% Calculation of dy_c/dx for Values of Different x
if x>= 0 && x<=P;
     dy_c1_dx = (M/P^2)*(2*P-2*x); % This is the Gradient if 0<=X and X<=P
  elseif x>=P && x<=1;
      dy_c2_dx = (M/(1-P)^2)*(2*P-2*x); % This is the Gradient if P<=X and X<=1
  end
sum1 = 0;
sum2 = 0;
for i = 1:n
      if x>=0 && x<= P;
           sum1 = sum1+(dy_c1_dx);
           S_0(i) = sum1;
           sum2 = sum2+(dy_c1_dx)*cos(theta);
          S_1(i) = sum2;
      elseif x> P && x<=1;
          sum1 = sum1+ (dy_c2_dx);
          S_0(i) = sum1;
          sum2 = sum2 + (dy_c2_dx)*cos(theta);
          S_1(i) = sum2;
      end
  end