plot graph for nested if

Question

liyana nadirah 2020-1-27

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/502080-plot-graph-for-nested-if

评论： liyana nadirah 2020-1-28

l=input('l=');
for t=0:100
    if t>2
        g=((3/(309*0.0014))*((((0.0000126*(t-2))/l)*80.4)-(l/6)));
    elseif t>80
        g=l-((80.4/309)*exp(((((-3*0.0000126)/(0.0014*l))*(t-80)))));
    else
        g=0;
    end
    disp (g);
end
t=0:100;
plot (t,g)

can someone explain how to plot graph using this coding because the don't get the graph.

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liyana nadirah 2020-1-27

*the graph not show.

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Answer 1

Bhaskar R 2020-1-27

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/502080-plot-graph-for-nested-if#answer_412146

在 MATLAB Online 中打开

l=input('l=');
g =  zeros(1, length(0:100));% initialize g with 0's of length t
c = 1; % counter variable
for t=0:100
    if t>2
        g(c)=((3/(309*0.0014))*((((0.0000126*(t-2))/l)*80.4)-(l/6)));
    elseif t>80
        g(c)=l-((80.4/309)*exp(((((-3*0.0000126)/(0.0014*l))*(t-80)))));
    else
        g(c)=0;
    end
    c = c+1; % increment counter variable
    disp (g);
end
t=0:100;
plot (t,g)

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Walter Roberson 2020-1-28

在 MATLAB Online 中打开

for t=0:100

t is a scalar

if (t(d)>2) && (t(d)<=80)

d is undefined. If d does not happen to be 1, then because t is a scalar, t(d) would be out of range.

for l=0.0002:0.001

every iteration of that loop, every different value of l, you are ovewriting all of g. The result would be the same as if you had only done the last of them, 0.0002 .

Notice by the way that because the default increment is 1, your code

for l=0.0002:0.001

is the same as

for l=0.0002 : 1 : 0.001

so 0.0002 would be used, then 0.0002+1 would be examined and found to be greater than 0.001 so the loop would stop.

liyana nadirah 2020-1-28

emmm sorry idon't get it, so

first i should declare d as 1?

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Answer 2

Walter Roberson 2020-1-27

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/502080-plot-graph-for-nested-if#answer_412155

编辑：Walter Roberson 2020-1-27

在 MATLAB Online 中打开

l = input('l=');
t = 0:100;
g = zeros(size(t));
mask = t>2 & t <= 80
g(mask) = ((3/(309*0.0014))*((((0.0000126*(t(mask)-2))/l)*80.4)-(l/6)));
mask = t>80;
g(mask) = l-((80.4/309)*exp(((((-3*0.0000126)/(0.0014*l))*(t(mask)-80)))));
plot (t,g)