My elseif condition is never checked. What to do?

Hello,

I want to ask a very noob question: My elseif condition is never checked. What to do?

Why do I ask this?

So, let me explain.

I got this piece of code:

A = [0.4 1.2 0.5 0.7 0.2 0.6];
S = [2.0 0.7 0.2 1.1 3.7 0.6];
in(1) = 0.4;
out(1) = in(1)+S(1);
list = 0;

%calculation of ins vector
for i = 2:6
    in(i) = in(i-1)+A(i);
    %calculation of outs vector
    for j = 2:6
        out(i) = max(out(i-1),out(i))+S(i);
    end
end

So, this program simulates the inputs and outputs in/from a server

Inputs(in) and outputs(out) are already calculated in above for

The idea is simple: if an input is done in server, list will increment by 1, if an output is done from server it will decrement by 1

A way to do this is to compare if, on time axe, we have inputs in server or outputs from it and to increment and decrement accordingly

Here everything I think looks clear for me, I know how to make those ifs

But the big challenge for me is to see the evolution of the list on a plot

So, I wrote this piece of code

i = 1; %ins
o = 1; %outs
n = 1; %every for iteration

for r = 0:0.1:12
    if r == in(i)
        list = list + 1;
        i = i + 1;
    elseif r == out(o)
        list = list - 1;
        o = o + 1;
    end
    list1(n)=list;
    n = n + 1;
end
plot(l1,'-r')

ylabel('list')
xlabel('time')
grid;

My plot looks like this:

Which is I intended, but it looks like the graph will never decrement, it will not go in elseif part.

What can I do in order to make my plot to go down ( to check that elseif as well ) in order to make it work on my plot?

List stores how many clients are not in server ( because one client is in there )

Time stores how much time did server had to take for each client

If I am unclear in what I am asking for, you can ask me to clear some things up.

Thank you for any kind of help.

Answer 1

[Image Analyst]

To compare floating point numbers, you need to use ismembertol(), not ==.

Like

if ismembertol(r, in(i), .0001)

See the FAQ: https://matlab.fandom.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

[Laurian Hurduza]

Thank you for your help!

I modified the code above, and I have something that looks like this:

i = 1; %ins
o = 1; %outs
n = 1; %every for iteration
for r = 0:0.1:12
    if ismembertol(r, in(i), .0001)
        list = list + 1;
        i = i + 1;
    elseif ismembertol(r, out(o), .0001)
        list = list - 1;
        o = o + 1;
    end
    list1(n)=list;
    n = n + 1;
end
plot(l1,'-r')
ylabel('list')
xlabel('time')
grid;

But I recieve the following error:

Index exceeds the number of array elements (6).

Error in ex1 (line 28)
    if ismembertol(r, in(i), .0001)

I just changed my conditions from

if r == in(i)

in

if ismembertol(r, in(i), .0001)

My array elements are 6, but the weird thing is that the code worked with wrong condition, but with the correct one, it doesn't..

What to do in this case?

[Image Analyst]

Please give us a script that runs, or at least plots. When I run your code, I get a error and there is no plot:

clc;    % Clear the command window.
fprintf('Beginning to run %s.m ...\n', mfilename);
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;

A = [0.4 1.2 0.5 0.7 0.2 0.6];
S = [2.0 0.7 0.2 1.1 3.7 0.6];
in(1) = 0.4;
out(1) = in(1)+S(1);
list = 0;

%calculation of ins vector
for i = 2:6
    in(i) = in(i-1)+A(i);
    %calculation of outs vector
    for j = 2:6
        out(i) = max(out(i-1),out(i))+S(i);
    end
end
i = 1; %ins
o = 1; %outs
n = 1; %every for iteration

for r = 0:0.1:12
    if r == in(i)
        list = list + 1;
        i = i + 1;
    elseif r == out(o)
        list = list - 1;
        o = o + 1;
    end
    list1(n)=list;
    n = n + 1;
end
plot(l1,'-r')

ylabel('list')
xlabel('time')
grid;

fprintf('\nDone running %s.m ...\n', mfilename);