Help regarding Use of basic loop in matlab

[abaqusian]

Hi everybody,

At present, I am learning to work with matlab. I want to learn how to implement a basic loop for the following steps I perform.
I have an excel file named "book" in format (.xlsx). I have two columns with ten rows each as shown below :

serial  value  
1        0.15
2        0.20
3        0.52
4        0.24
5        0.05
6       -2.05

What I want to do ?

(i) Read the excel file in xlsx into matlab
(ii) For first 3 values in Column_1 , multiply with value 2 and Assign to a new array. Lets say array as "a"
(iii)For last 3 values in column_1 , multiply with value 3 and Assign to a new array. Lets say array as "b"
(iv) Concatenate the new arrays "a" and "b" into a single array . Lets say array as "c"
(v) Assign a new array for column_2 of the excel file, assign an array "d"
(vi) plot array "c" vs "d"

What I did ?

data=xlsread('book');
a=data(1:3,1)*2;
b=data(4:6,1)*3;
c=[a;b];
d=data(:,2);
plot(c,d)

What I wish to do ?

How to implement a loop to automate this process instead of writing separate syntax as I have did above . How to get to the same result with a use of loop in matlab ?

Kindly cast your opinion to optimise the process.

Thanks from Basic Matlab Learner

 

[abaqusian]

Additional information :

Since, I work with large number of values (row wise) in Excel sheet in a single column , I want to multiply every 10 values in column1 with a factor , then next 10 values in column1 with an another factor And SO ON . I want to do this in a loop.

 

[LiteYear]

While a loop would certainly help, I read somewhere that if you're using a loop in Matlab you're probably doing it wrong. I thus offer this non-loop suggestion:

factors = [2 3]; % specify your multiplicative factors
every = 10; % specify the number of rows to apply each factor to

factors = repmat(factors, 1, every)'(:); % repeat, transpose and serialise the factors to form a column vector of factors

c = data(:,1).*factors
d = data(:,2)
plot(c,d)