plot graph for nested if

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.

[liyana nadirah]

*the graph not show.

Answer 1

[Bhaskar R]

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)

[liyana nadirah]

i get the graph but the data output is repeated. why?

[Bhaskar R]

Your data is according to your statements and you have used disp(g) to print g for each iteration that is why data output is repeated.

[liyana nadirah]

so should i delete the comand disp g

[Walter Roberson]

Yes. Or use logical indexing like I posted

[liyana nadirah]

for l=0.0002:0.001
g =  zeros(1, length(0:100));% initialize g with 0's of length t
c = 1;% counter variable
    for t=0:100
        if (t(d)>2) && (t(d)<=80)
            g(c)=((3/(309*0.0014))*((((0.0000126*(t-2))/l)*80.4)-(l/6)));
        elseif t(d)>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
    end
end
disp (g)
t=0:100;
plot(t,g)
xlabel('Day')
ylabel('Cumulative percentage of nutrient release,%')

how about this can you help me fix my nested for loop. and how can i have all the graph for all 'l' in one graph

[Walter Roberson]

    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]

emmm sorry idon't get it, so

first i should declare d as 1?

Answer 2

[Walter Roberson]

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)