Index exceeds matrix dimension in a for loop?

Question

lauuser1 2016-3-3

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/271146-index-exceeds-matrix-dimension-in-a-for-loop

回答： Stalin Samuel 2016-3-3

function[pos_N] = func(v_0, windspeed)
pos_N(1,1) = 0; %initial distance
pos_N(1,2) = 500; %initial elevation
%loop starts here
v = v_0;
theta = 20;
g = 9.81;
for t=0:0.1:1000
    horiz_velocity = v*cos(theta)+windspeed;
    vert_velocity = v_0*sin(theta)+g*sin(theta)*t;
row_number = 1+10*t;
if t==0
else
    pos_N_(row_number,1) = pos_N((row_number-1),1)+horiz_velocity*0.1; %position horizontal
    pos_N_(row_number,2) = pos_N((row_number-1),2)-vert_velocity*0.1; %elevation decreases because he descends down

... and there is more to the code but at those last two lines, the code has the error "index exceeds matrix dimension".

Why? I have not defined any set size for the matrix pos_N.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Stalin Samuel 2016-3-3

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/271146-index-exceeds-matrix-dimension-in-a-for-loop#answer_212104

在 MATLAB Online 中打开

function[pos_N] = func(v_0, windspeed)
pos_N = zeros(max(1+10*(0:0.1:1000)),2);%matrix initialization
pos_N(1,1) = 0; %initial distance
pos_N(1,2) = 500; %initial elevation
%loop starts here
v = v_0;
theta = 20;
g = 9.81;
for t=0:0.1:1000
    horiz_velocity = v*cos(theta)+windspeed;
    vert_velocity = v_0*sin(theta)+g*sin(theta)*t;
row_number = round(1+10*t);
if t==0
else
    pos_N_(row_number,1) = pos_N((row_number-1),1)+horiz_velocity*0.1; %position horizontal
    pos_N_(row_number,2) = pos_N((row_number-1),2)-vert_velocity*0.1; %elevation decreases because he descends down