Output Matrix in For Loop duplicates. Why?

hi, I have a text file which I unpacked using importdata, and then quads.

M = importdata('Textfile.txt');
quads = M.data;
x = length(quads);

for i=1:x-1
    quads(i)=quads(i+1)-quads(i);
    P(i)= quads(i)/60;  

end

the output is duplicated.

it will say

quads =

value
value
value

quads = 

value
value
value

quads = 

value
value
value

Is this because the TextFile.txt is a double array (as it says in Workspace) when I unpack it in Matlab?

----

A second question is I am trying to add up the differences in all the values and ultimately get the final value. How can I do this using a For Loop?

For ex; if the textfile contains

3
6
8
10
12

The differences between 3-0 = 3, 6-3 = 3, 8-6=2, and so forth..

3
3
2
2
2

Sum of all these = 12. The final value. What code can I add to my For Loop above?

Answer 1

[KALYAN ACHARJYA]

In the second case, you can do this way

A=[3 6 8 10 12];
B=[0;A'];
sum1=0;
[rows colm]=size(B);
for i=1:rows-1
   sum1=sum1+B(i+1,:)-B(i,:);
end
disp(sum1);

Command Window

>> 12

Recommended: There may another method to do the same without using a loop. (logical indexing)

[FanOf23]

Your command worked, thank you. How can i make it so that the output (12) is in a new matrix?

[KALYAN ACHARJYA]

   sum1=[sum1]; 
   disp(sum1);

[Walter Roberson]

We recommend that you not use sum as the name of a variable. If you get in the habit of using sum as the name of a variable, it is pretty much inevitable that at some point in code after you have made sum into a variable, that you will try to invoke sum() as a function.

[KALYAN ACHARJYA]

@Walter Sir Thanks #Gratitude