Why do I get error incorrect use of '=' operator?

Question

현우 이 2020-6-19

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https://ww2.mathworks.cn/matlabcentral/answers/551119-why-do-i-get-error-incorrect-use-of-operator

评论： 현우 이 2020-6-19

I made the drunk man simulation. But if I run this, I get the error message Error: Incorrect use of '=' operator. To assign a value to a variable, use '='. To compare values for equality, use '=='.

and if I change = to <=, I get the error message

while (s<10 && s >-10 && i<100)

↑

Error: Illegal use of reserved keyword "while".

Why does this happen and how can I fix it? Thanks a lot in advance.

This is my code.

alive = 0
success = 0
dead = 0
p = 0.5
for n=1:1000
{
i = 0
s = 0
while (s<10 && s >-10 && i<100)
x = rbinom(1, 1, p);
if(x == 1)
s = s-1;
else
s = s+1;
i = i+1;
end
if(s == 10)
success = success + 1;
end
if(s == -10)
dead = dead + 1;
end
end
if(s<10 &&s > -10)
alive = alive +1;
end
barplot(c(success, dead, alive))

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Answer 1

Nipun Agarwal 2020-6-19

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此回答的直接链接

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在 MATLAB Online 中打开

Hey,

The problem comes in because of curly braces after the for loop. MATLAB syntax never allows curly braces after the for loop. I have updated the code of yours and indented it properly for you to have a better standing.

alive = 0;
success = 0;
dead = 0;
p = 0.5;
for n=1:1000
    i = 0;
    s = 0;
while (s<10 && s >-10 && i<100)
    x = 1;
    if(x == 1)
        s = s-1;
    else
        s = s+1;
        i = i+1;
    end
end
if(s == 10)
    success = success + 1;
end
if(s == -10)
    dead = dead + 1;
end
if(s<10 &&s > -10)
    alive = alive +1;
end
end
barplot(c(success, dead, alive))

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Stephen23 2020-6-19

在 MATLAB Online 中打开

The MATLAB Editor's default indentation rules give this even clearer version:

alive = 0;
success = 0;
dead = 0;
p = 0.5;
for n=1:1000
    i = 0;
    s = 0;
    while (s<10 && s >-10 && i<100)
        x = 1;
        if(x == 1)
            s = s-1;
        else
            s = s+1;
            i = i+1;
        end
    end
    if(s == 10)
        success = success + 1;
    end
    if(s == -10)
        dead = dead + 1;
    end
    if(s<10 &&s > -10)
        alive = alive +1;
    end
end
barplot(c(success, dead, alive))