MATLAB: How to use a for loop to calculate the sum of a row vector

for loop

I have the values x-[1, 23, 43, 72, 87, 56, 98, 33] How do you calculate the sum (which should equal 413) using a for loop?

Best Answer

x = [1, 23, 43, 72, 87, 56, 98, 33] ;
y = 0;
for n = 1:length(x)
    y = y + x(n);
end

Related Solutions

MATLAB: I need to know how to sum to the values of a specific column (identified by an index that can vary) of a generic matrix, a given column vector. For instance, how i decrease by 1 all the values of a column in a matrix (the rest remains the same)

Your question is rather confusing, as you seem to pose two different questions. I address both of these below:

>> A = magic(10)
A =
    92    99     1     8    15    67    74    51    58    40
    98    80     7    14    16    73    55    57    64    41
     4    81    88    20    22    54    56    63    70    47
    85    87    19    21     3    60    62    69    71    28
    86    93    25     2     9    61    68    75    52    34
    17    24    76    83    90    42    49    26    33    65
    23     5    82    89    91    48    30    32    39    66
    79     6    13    95    97    29    31    38    45    72
    10    12    94    96    78    35    37    44    46    53
    11    18   100    77    84    36    43    50    27    59
>> col = 6;
>> sum(A(:,col)) % the sum of one column
ans =  505
>> A(:,col) = A(:,col)-1 % decrease all values in one column
A =
    92    99     1     8    15    66    74    51    58    40
    98    80     7    14    16    72    55    57    64    41
     4    81    88    20    22    53    56    63    70    47
    85    87    19    21     3    59    62    69    71    28
    86    93    25     2     9    60    68    75    52    34
    17    24    76    83    90    41    49    26    33    65
    23     5    82    89    91    47    30    32    39    66
    79     6    13    95    97    28    31    38    45    72
    10    12    94    96    78    34    37    44    46    53
    11    18   100    77    84    35    43    50    27    59

MATLAB: I have no idea how to do this

You were very close, actually. A couple of things. One is, Sum holds your sum, so don't treat it like a vector by indexing into it. Second is your conditional. You want to only go through the loop while Sum is LESS than 3500, not greater! Since you showed some good effort, I will help you out by fixing these simple errors. Study the code to see what does what.

Y = [95 93 69 75 74 88 83 91 90 78 89 88 86 79 80 55 32 100 97 81 70 ...
    75 77 96 83 86 74 91 89 92 79 70 83 88 91 100 76 41 73 71 79 94 ...
    105 92 89 89 87 66 94 97 92 78 84 89 ];
Sum = 0; ctr = 0;
while Sum <= 3500
    ctr = ctr + 1;
    Sum = Sum + Y(ctr);
end
Y(ctr)
Sum

Best Answer

Related Solutions

MATLAB: I need to know how to sum to the values ​​of a specific column (identified by an index that can vary) of a generic matrix, a given column vector. For instance, how i decrease by 1 all the values ​​of a column in a matrix (the rest remains the same)

MATLAB: I have no idea how to do this

Related Question

MATLAB: I need to know how to sum to the values of a specific column (identified by an index that can vary) of a generic matrix, a given column vector. For instance, how i decrease by 1 all the values of a column in a matrix (the rest remains the same)