# ReIndexing a Series(non-infinite)

• jack612blue
In summary, the conversation discusses a mathematical problem where the upper and lower limits have been decreased by 2. The question of how to relate two variables, k and j, in order to change the starting point of the series is also brought up. The solution involves using algebraic substitution and replacing k with i+2 in the formula for the terms of the series. The conversation ends with the suggestion to replace i with k to complete the required solution.
jack612blue

## The Attempt at a Solution

#7 only
I'm stumped, i have no idea as to what to do.

I can't even find help on the internet/book. Its almost like this topic doesn't even exist.

I know both upper and lower limits have been decreased by 2

jack612blue said:

## The Attempt at a Solution

#7 only
I'm stumped, i have no idea as to what to do.

I can't even find help on the internet/book. Its almost like this topic doesn't even exist.

I know both upper and lower limits have been decreased by 2

Ok, then also change k to k+2. Doesn't that make sense? It would offset the other change.

Last edited:
Dick said:
Ok, then also change k to k+2. Doesn't that make sense? It would offset the other change.

Hello,

Thank you for responding.

I understand that part

6
sigma
1

I'm just confused as to what to put in the inside.

I found this on wikipedia. is this relevant?

Define a new variable, say, j. How should j and k be related so that j goes from 1 to 6 when k goes from 3 to 8?

jack612blue said:
I found this on Wikipedia. Is this relevant?

Yes, it's relevant .

It's really just an algebraic substitution. The series, as given, starts with k= 3 and we want to change that to a series starting at 1. Rather than use "k" to mean two different things, I am going to call this second index "i". That is, we want i= 1 to correspond to k= 3. That is the same as saying k- i= 3- 1= 2 so that k= i+ 2 or i= k- 2.

When k= 8, i= 8- 2= 6 so the series goes from i= 1 to 6 as desired. And in the formula for the terms of the series, since, as above, k=i+ 2, replace each k with i+ 2. d What do you get when you replace "k" in "2k- 1" with "i+2"?

You will get a series in i. Since the "index" is a dummy, and has no meaning in the total sum, you can, to completely match what is required, simply replace "i" with "k" again.

## 1. What is the purpose of reindexing a series?

Reindexing a series allows you to change the order, add or delete elements, or fill in missing values of the index of a series. This can be helpful when you need to align multiple series with different indexes or when you want to perform arithmetic operations between two series.

## 2. How do you reindex a series in Python?

To reindex a series in Python, you can use the reindex() method. This method takes in a new index and returns a new series with the specified index. You can also use the method parameter to specify how you want to handle missing values.

## 3. Can you reindex a series with non-numeric indexes?

Yes, you can reindex a series with non-numeric indexes. The reindex() method in Python accepts any type of index, including strings, dates, and custom objects.

## 4. Will reindexing change the values in the series?

No, reindexing does not change the values in the series. It only changes the order or adds new indexes to the series. If there are missing values in the new index, they will be filled with NaN or the specified fill value.

## 5. Is reindexing a series the same as sorting the series?

No, reindexing and sorting a series are two different operations. Reindexing changes the order of the series, while sorting rearranges the series based on the values of the index or the data. Reindexing can also add or delete elements, while sorting only changes the order of existing elements.

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