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while loops with and conditions (repeat until conditions are met)

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Mariam Al Zarouni 2020-4-7

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评论： Mehmed Saad 2020-4-8

Hello everyone

I'm not the best in coding but i'm trying hard. So basically, i need a code where i can prompt the user to enter any random, real, and positive value only.(number of values must be EVEN).

For example:

the user would enter: 1 4 5

the output would be: re-enter your values as their number must be even

the user would re-enter: 1 4 5 3

and the loop will continue in this case

I hope you got my point and could assist me hence i'm really struggling and haven't got much time

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Alex Mcaulley 2020-4-7

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What have you tried? Can you show your code?

Walter Roberson 2020-4-7

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http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

Hint: length() and mod()

Mehmed Saad 2020-4-7

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if user is going to eneter like

1 4 5

in that case you have to use input('prompt','s')

Mariam Al Zarouni 2020-4-7

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So basically i've tried many codes.

First code: ( the user enters two values only, values should be real)

the problem with this code is that i get ability to type in my input but when i press enter afterwards, i get this red long message saying "Error: Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax error. To construct matrices, use brackets instead of parentheses."

Resistor=input('Enter values [R1...Rn]');
[row,column]=size(Resistor)
while isreal(Resistor) && row==1 && column==2
end
fprintf('-------------------\n\n')

Mehmed Saad 2020-4-7

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Resistor=input('Enter values [R1...Rn]');

now in cmd what you are doing is directly entering two numbers like this

1 2

which will lead to

Error using Untitled4 (line 1)
Error: Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax error. To
construct matrices, use brackets instead of parentheses.

if you enter

[1 2]

i.e. put braces to make it an array no error will occur

a second way is to use string input but that'd be a bit complex

Mariam Al Zarouni 2020-4-7

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Another code was this: I get the same error here too. I also want to add another condition in the while loop which is the number of value must be even as i mentioned earlier but i didn't know where or how to put it. I know for even m(m,2)==0

close all;
Resistors=input(' Enter values of two resistances in ohm [R1 R2]= '); % to enter the values of the resistors
Total=length(Resistors);
[row,column]=size(Resistors);% matrix of the resistors
if isreal(Resistors) && row==1 && column>=2 % this is to make sure the values are real and the matrix is one row and infinite number of columns (values)
for number=1:Total
if Resistors(number)>0 % value of the resistor is positive or otherwise
equation=true;
else if Resistors(number)<=0
equation=false;
break;
end
end
end
end
if equation==false
disp(' invalid numbers .... please enter valid numbers')
end
end
disp ('===================================================================')