Given a large number n

When I say n my elements will be {1,2,3,4..n}

take n, k where k will be 2 or 3

Picking up k  element subsets 

In such a way it will return one subset at a time without storing in list to avoid memory usage more 

A for loop like 

Some place within the code where 

 I will be able to perform my task using  each 2 or 3 element subset

and later forget about it

If we go for function may be we need to go for recursive function in such a way that at each call of function it will produce one 2 element subset I do my work with that and then do my next call of the same function again

Kind help please 

Given a excel sheet with data for regression as input column Y will be a dependent variable 

Say a maximum of 120 independent variables are their 

A function that takes excel as input with headers as in the excel file

Do pick all possible subsets of maximum size 5 that is sizes 2,3,4,5 only 

Pick each and eleminate not to store them all together as otherwise storage will be a problem if more data

Copy only those subsets of independent variables to seperate seperate sheet

Only those subsets 

where the variables are independent pairwise between them

Step 2 function 

Then need to run a multiple linear regression on these subsets like training and test 

And choose the best models I each of cases of number of variable

That is best with 2 variables

Again with 3 variables

Similarly 4 and 5

Atleast if possible upto 2 to 3 variables it will be good kind help with your guidance and what is possible 

If you are not able give the program of train test regression with charts no issues 

Kind help with atleast storing the independent pairwise subsets of size 2 and 3 into seperate sheets in a Excel file atleast

I will do the regression at my end 

I will have excel sheet with minium 500 coulmns and 1000 rows say

For sample to explain my question I attach a demo excel

All my columns have headers

I am looking to find all 2 way multiplication and add them as columns to my excel sheet and return it as a new excel sheet say

The column names for the new 2 way column should be like the

header name of column you are multiply * the name of the other columsn

Now in sample file if i multiple column with name A with column with name B I get a new column with header A*B the header name should be inserted and

Below that all the elements of that A column multiplied  with that of B should come

I am looking to form columns for all possible2  way multiplication for the excel I will give.

As you can see the demo file

Excel_to_explain.xlsx

Kind help please

Kind help to implement the attached flowchart

Finding_Detour_using_alorigthm.pdf

Given a graph G and a vertex v find the shortest self returning walk from that visits all vertices starts at v and comes back to v.

In the below graph the shortest self returning walk which visits all vertices and comes back to first to started vertex

A function which takes a graph G  and  vertex v as input and returns the length of the  shortest self returning walk of that vertex in the below example 10

I am sorry for the error i just saw the change after reading more in deep

For the vertex 7 the shortest self returning walk from that visits all vertices starts at 7 and comes back to 7 It is a walk so edges can repeat

The closed walk which passes through all vertices minimum from vertex 7 is so length 10. is what it means

so it returns 10.