Combine two Lists into one

Questions
1

I searched and couldn’t find a similar topic but I assume this has to exist so I apologize if this is a duplicate. I am collecting numbers on Screen 1, 2, and 3. I can aggregate the numbers (from one screen) into a list on screen 4 and create a dotplot. Can I aggregate across all three screens easily - I don’t believe the ‘and’ function works since they are numbers and not booleans.

2

Our graph team is AMAZING and has a function for that:

C_{oncat}\left(L_1,L_2\right)=\sum_{n=\left[1...\operatorname{length}\left(L_1\right)+\operatorname{length}\left(L_2\right)\right]}^{\left[1...\operatorname{length}\left(L_1\right)+\operatorname{length}\left(L_2\right)\right]}\left\{n\le\operatorname{length}\left(L_1\right):L_1\left[n\right],L_2\left[n-\operatorname{length}\left(L_1\right)\right]\right\}

Just paste into a graph expression line and either create your lists or change the references in the function. Credit @aknauft

1 Like
3

I’ve used this example to help with ideas in the past. Would the Concatenate Lists folder work as well?

https://www.desmos.com/calculator/mwffimho5u

4

That. Is. Amazing!

Thank you so much!

5

You could leave x_1 in the table as just 1 and make a second column in your table for T_emp1.

6

Thank you so much for posting this!! I’ve been looking for this feature for years, and I just stumbled across this post. Keep up the great work!

1 Like
7

This “Advanced Lists” folder includes an example of how to sort a list from least to greatest. Can you modify it so it sorts from greatest to least?

8

In A_sorted, use this for the second parameter instead:

\left[1,1-\frac{1}{\operatorname{length}\left(A\right)-1}...,0\right]

I have my own list functions here (finding the index of a value has a function now I believe, so obsolete):

https://www.desmos.com/calculator/wbdncnszny

1 Like
9

If I wanted to join 5 lists, how do I modify this:

L=\sum_{n=\left[1…\operatorname{length}\left(L_{1}\right)+\operatorname{length}\left(L_{2}\right)\right]}^{\left[1…\operatorname{length}\left(L_{1}\right)+\operatorname{length}\left(L_{2}\right)\right]}\left{n\le\operatorname{length}\left(L_{1}\right):L_{1}\left[n\right],L_{2}\left[n-\operatorname{length}\left(L_{1}\right)\right]\right}

thanks

10

If I wanted to join 5 lists, how do I modify this:

L=\sum_{n=\left[1…\operatorname{length}\left(L_{1}\right)+\operatorname{length}\left(L_{2}\right)\right]}^{\left[1…\operatorname{length}\left(L_{1}\right)+\operatorname{length}\left(L_{2}\right)\right]}\left{n\le\operatorname{length}\left(L_{1}\right):L_{1}\left[n\right],L_{2}\left[n-\operatorname{length}\left(L_{1}\right)\right]\right}

thanks

11

There is a join function now that didn’t exist before. So you can just use something like L = join(list1,list2,…)

2 Likes
12

One thing I’ve noticed is that Desmos makes it a bit cumbersome to deal with lists of points or parametric functions when using summation to manipulate lists.

For instance, to concatenate two lists of points L1, L2, you’d have to concatenate them component-wise. So instead of
L3 = Concat(L1,L2)
that would be
L3 =(Concat(L1.x,L2.x),Concat(L1.y,L2.y))

Oh, except I overlooked the join function mentioned here that can deal with both lists of numbers and lists of points or parametric functions.