Matrix dimensions must agree

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Kolleggerm1 2019-10-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/484103-matrix-dimensions-must-agree

评论： Star Strider 2019-10-9

I am using Forward Euler to solve based on the given condtions that H'=(S-S(f))/(1-F^2) F^2=(q^2)/(gH^3) S(f)=C(f)F^2 and H(x(1))=H(1).

I am getting the error "Matrix dimensions must agree" for line 17.

What does that mean?

clc; clear all;
h=1000; % step size
xmin=-10000;
xmax=10000;
x=xmin:h:xmax; %x boundaries
n=length(x);
y=zeros(1,n);% Initial condition
x0=0;
q=10;
s=0.00025;
H(1)=30;
Cf=.00200;
g=9.8;
i=1:n-1;
F=sqrt((q^2)/(g*H^3));
s(i+1)=Cf*(F);
dH=(s-s(i+1))/((1-F));
for i=1:n-1
    x(i+1)=i*h;
    y(i+1)=y(i)+h*dH;
end
figure
hold on
plot (x,y,'r', 'linewidth',2)
xlabel ('Channel Distance(m)')
ylabel ('Water Elevation(m)')
title ('Water Elevation vs Channel Distance')

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Star Strider 2019-10-9

在 MATLAB Online 中打开

Kolleggerm1’s Answers moved here —

First:

h=1000;
xmin=-10000;
xmax=10000;
x=xmin:h:xmax;
n=length(x);
H=zeros(1,n);
x0=0;
q=10;
s=0.00025;
H(1)=30;
Cf=.00200;
g=9.81;
i=1:n-1;
slope=(s-(Cf(q.^2)/(g(H(i).^3))))/(1-((q.^2)/(g(H(i).^3))));
for i=1:n-1
    x(i+1)=x(i)-h;
    H=H(i-1)-slope*h;
end
figure
hold on
plot (x,H,'r', 'linewidth',2)
xlabel ('Channel Distance(m)')
ylabel ('Water Elevation(m)')
title ('Water Elevation vs Channel Distance')