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Add to matrix missing elements (for list of time series)

This question is an extension of the 43122. I’ve looked through many interesting post (like this) but (as always) missed the direct matching. So the setting is simple: ...
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Combining more than two lists by first column as index

Please bear with me. It might be easy but its been hard for me. I have say three lists: ...
242 views

Join lists of lists with unique id

Sorry for the vague title, but I can't describe my problem properly and shortly. I am maintaining a list of players and their games with the following form: ...
168 views

Deleting elements on a list by the first element of another list

I was trying to make this L1 = {{2, 1}, {6, 4}, {8, 7}, {9, 5}}; L2 = {{2, 9}, {9, 6}}; L = Union[L2 , L1] And I used this: ...
566 views

Can someone explain this code for joining two lists by the first element of each sublist?

Background (which may be skipped, unless context is needed) I've recently begun learning Mathematica (and only up to chapter 3 of Wellin), but wanted to write some code to get a better feel for ...
487 views

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Is there any way to instruct Complement to skip the sorting part? If the answer is no (likely), the next question would be: how can I remove from a sorted list ...
339 views

Combining the items with common available dates from two lists [duplicate]

I have two lists of data including dates such as data1 = {{{yy, mm, dd}, a}, ...} data2 = {{{yy, mm, dd}, A}, ...} There are some missing dates from each list, ...
180 views

joining lists based on content

I have lists created by other processing steps, which are basically constituted by elements like this: ...
8k views

How to efficiently find positions of duplicates?

Is there an efficient way to find the positions of the duplicates in a list? I would like the positions grouped according to duplicated elements. For instance, given ...
824 views

Counting the population of integers

Suppose that myData is a list of sublists. Each sublist has a length of one or greater and contains any number of replicates of the integers 1, 2, 3, and 4. I ...
194 views

All values for a function with two arguments without Outer

Given two lists $l_a = \{a_1, a_2, a_3\}$, $l_b = \{b_1, b_2, b_3, b_4\}$ and some function $f$ accepting two arguments, how can I produce a list of all values $f(a, b)$ for $a\in l_a$ and $b \in l_b$ ...
2k views

Combining two lists [duplicate]

Possible Duplicate: How do I obtain an intersection of two or more list of lists conditioned on the first element of each sub-list? I would like to combine two lists. ...