Make a vector out of all even/odd numbers from 1 to 100 using for and if

Question

The Canary Cry 2018-3-15

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回答： sebastian Muñoz Aponte 2020-7-27

Hello, I'm to make two vectors: one consisting of all even numbers between 1 and 100 and one of all the odd numbers. I have to use only simple for and if cycles.

My attempt:

j=1;
k=1;
for i=1:100
    if mod(i,2)==0 && i~=1
        even(j)=i;
        j=j+1;
    else
        odd(k)=i;
        k=k+1;
    end
end
even
odd

Now the odd part works well but the even part doesn't. This is what it prints out:

Columns 1 through 22
     2     4     6     8    10    12    14    16    18    20    22    24    26    28    30    32    34    36    38    40    42    44
Columns 23 through 44
    46    48    50    52    54    56    58    60    62    64    66    68    70    72    74    76    78    80    82    84    86    88
Columns 45 through 66
    90    92    94    96    98   100    51    52    53    54    55    56    57    58    59    60    61    62    63    64    65    66
Columns 67 through 88
    67    68    69    70    71    72    73    74    75    76    77    78    79    80    81    82    83    84    85    86    87    88
Columns 89 through 100
    89    90    91    92    93    94    95    96    97    98    99   100

So it prints all even numbers, which is great, but then it prints every number from 51 to 100. Why? When I type in mod(51,2) it says 1 so the condition doesn't apply.

(Posted on here a couple of minutes ago, hope that's allowed)

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Answer 1

James Tursa 2018-3-15

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编辑：James Tursa 2018-3-15

在 MATLAB Online 中打开

You probably have left-over variables from a previous run that you are writing into. Clear them out first. E.g., put this at the top of your code:

clear even odd

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James Tursa 2018-3-15

在 MATLAB Online 中打开

Scripts run in your current workspace and leave all resulting variables in your workspace. Sometimes this is what you want, but often it is not. I very seldom use scripts ... almost everything I write is a function, even if it takes no inputs. That way I know I am starting with a fresh workspace for the new code and that I am not corrupting my current workspace. E.g., if your code had been in a file called even_odd.m like this:

function even_odd
% your code
end

you would not have encountered the error that you did. Then if you wanted it to operate on an arbitrary n value and return a result, it is easy to modify. E.g.,

function [even,odd] = even_odd(n)
    :
for i=1:n
    :
end

Etc.

The Canary Cry 2018-3-15

Right, I see. Thanks

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Answer 2

K. KARTHIK KUMAR 2019-12-16

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Create a vector of all the odd positive integers smaller than 100 in increasing order and save it into variable odds.
Create a vector of all the even positive integers smaller than or equal to 100 in decreasing order and save it into variable evens.

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Sena Yildirim 2020-4-17

did you have this questions answers?

Ayush Khandelwal 2020-5-9

Answer for even number fast

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Answer 3

Lenny C 2020-1-27

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For doing the even part initialize the value of k=50 and change for statement to for i=100:-1:1 and change the value of k from k+1 to k-1(this prints even number in reverse order .