I have 2 arrays say
sum:
68
78
25
45
85
Index:
0
1
2
3
4
I did bubble sort on sum and got as:
25
45
68
78
85
Now, I need to know sort index array with respect to the sum array. So, my output of array should be:
2
3
0
1
4
How can I do that?
I'd recommend you sort the index array instead, and have the comparisons made using the values the indexes "point" to. So then you don't actually need to sort the "value" array just the "index" array.
So, here is a very simple solution that I never thought of and all credits goes to my project supervisor.. and it is.
Sort both the arrays under the same loop.. Thus when ever I will refer to any index, it will give me the sorted version.
Related
I have this data structure problem:
Implement an external sort method with two helper files. The separation
The initial file in chunks follows the following strategy: 20 elements are read from the file in chunks.
an array and are sorted with the internal sort method quicksort. Then it
writes the smallest element of the array to the auxiliary file and reads the next element from the
source file. If the element read is greater than the element written (it is part of the section
current), then it is inserted in order into the ordered subarray; otherwise it is added in
the free positions of the array. Because the elements of the array are extracted by the head
free positions remain on the opposite end. The section ends when the
sorted subarray is empty. To form the next section, start by ordering the array
(remember that the elements that were not part of the section were added to the array) and
then the process continues in the same way: write the smaller element to another file
helper and read element from the source file... Once the distribution is done, the phase of
mixing is the same as in the direct or natural mixing algorithms.
I'm thinking of this algorithm:
File origin
75
98
3
27
37
64
19
55
22
62
81
80
87
36
68
8
33
38
72
90
24
91
6
78
54
ordered array of 20 elements: 3-8-19-22-27-33-36-37-38-55-62-64-68-72-75-80-81-87-90-98
First element in the aux file 1: 3
After this point I don't know what the algorithm has to do to order the remaining 5 elements
I am new to array formulae and have noticed that while SUBTOTAL includes many functions, it does not feature COUNTIF (only COUNT and COUNTA).
I'm trying to figure out how I can integrate a COUNTIF-like feature to my array formula.
I have a matrix, a small subset of which looks like:
A B C D E
48 53 46 64 66
48 66 89
40 38 42 49 44
37 33 35 39 41
Thanks to the help of #Tom Shape in this post, I (he) was able to average the sum of each row in the matrix provided it had complete data (so rows 2 and 4 in the example above would not be included).
Now I would like to count the number of rows with complete data (so rows 2 and 4 would be ignored) which include at least one value above a given threshold (say 45).
In the current example, the result would be 2, since row 1 has 5/5 values > 45, and row 3 has 1 value > 45. Row 5 has values < 45 and rows 2 and 3 have partially or fully missing data, respectively.
I have recently discovered the SUMPRODUCT function and think that perhaps SUMPRODUCT(--(A1:E1 >= 45 could be useful but I'm not sure how to integrate it within Tom Sharpe's elegant code, e.g.,
=AVERAGE(IF(SUBTOTAL(2,OFFSET(A1,ROW(A1:A5)-ROW(A1),0,1,COLUMNS(A1:E1)))=COLUMNS(A1:E1),SUBTOTAL(9,OFFSET(A1,ROW(A1:A5)-ROW(A1),0,1,COLUMNS(A1:E1))),""))
Remember, I am no longer looking for the average: I want to filter rows for whether they have full data, and if they do, I want to count rows with at least 1 entry > 45.
Try the following. Enter as array formula.
=COUNT(IF(SUBTOTAL(4,OFFSET(A1,ROW(A1:A5)-ROW(A1),0,1,COLUMNS(A1:E1)))>45,IF(SUBTOTAL(2,OFFSET(A1,ROW(A1:A5)-ROW(A1),0,1,COLUMNS(A1:E1)))=COLUMNS(A1:E1),SUBTOTAL(9,OFFSET(A1,ROW(A1:A5)-ROW(A1),0,1,COLUMNS(A1:E1))))))
Data
I am new to using Julia and have little experience with the language. I am trying to understand how multi-dimensional arrays work in it and how to access the array at the different dimensions. The documentation confuses me, so maybe someone here can explain it better.
I created an array (m = Array{Int64}(6,3)) and am trying to access the different parts of that array. Clearly I am understanding it wrong so any help in general about Arrays/Multi-Dimensional Arrays would help.
Thanks
Edit I am trying to read a file in that has the contents
58 129 10
58 129 7
25 56 10
24 125 25
24 125 15
13 41 10
0
The purpose of the project is to take these fractions (58/129) and round the fractions using farey sequence. The last number in the row is what both numbers need to be below. Currently, I am not looking for help on how to do the problem, just how to create a multidimensional array with all the numbers except the last row (0). My trouble is how to put the numbers into the array after I have created it.
So I want m[0][0] = 58, so on. I'm not sure how syntax works for this and the manual is confusing. Hopefully this is enough information.
Julia's arrays are not lists-of-lists or arrays of pointers. They are a single container, with elements arranged in a rectangular shape. As such, you do not access successive dimensions with repeated indexing calls like m[j][i] — instead you use one indexing call with multiple indices: m[i, j].
If you trim off that last 0 in your file, you can just use the built-in readdlm to load that file into a matrix. I've copied those first six rows into my clipboard to make it a bit easier to follow here:
julia> str = clipboard()
"58 129 10\n58 129 7\n25 56 10\n24 125 25\n24 125 15\n13 41 10"
julia> readdlm(IOBuffer(str), Int) # or readdlm("path/to/trimmed/file", Int)
6×3 Array{Int64,2}:
58 129 10
58 129 7
25 56 10
24 125 25
24 125 15
13 41 10
That's not very helpful in teaching you how Julia's arrays work, though. Constructing an array like m = Array{Int64}(6,3) creates an uninitialized matrix with 18 elements arranged in 6 rows and 3 columns. It's a bit easier to see how things work if we fill it with a sensible pattern:
julia> m .= [10,20,30,40,50,60] .+ [1 2 3]
6×3 Array{Int64,2}:
11 12 13
21 22 23
31 32 33
41 42 43
51 52 53
61 62 63
This has set up the values of the array to have the row number in their tens place and the column number in the ones place. Accessing m[r,c] returns the value in m at row r and column c.
julia> m[2,3] # second row, third column
23
Now, r and c don't have to be integers — they can also be vectors of integers to select multiple rows or columns:
julia> m[[2,3,4],[1,2]] # Selects rows 2, 3, and 4 across columns 1 and 2
3×2 Array{Int64,2}:
21 22
31 32
41 42
Of course ranges like 2:4 are just vectors themselves, so you can more easily and efficiently write that example as m[2:4, 1:2]. A : by itself is a shorthand for a vector of all the indices within the dimension it indexes into:
julia> m[1, :] # the first row of all columns
3-element Array{Int64,1}:
11
12
13
julia> m[:, 1] # all rows of the first column
6-element Array{Int64,1}:
11
21
31
41
51
61
Finally, note that Julia's Array is column-major and arranged contiguously in memory. This means that if you just use one index, like m[2], you're just going to walk down that first column. As a special extension, we support what's commonly referred to as "linear indexing", where we allow that single index to span into the higher dimensions. So m[7] accesses the 7th contiguous element, wrapping around into the first row of the second column:
julia> m[5],m[6],m[7],m[8]
(51, 61, 12, 22)
Hi i have a 289x2 array that i want to sort in MatLab. I want to sort the first column into numerical ascending order. However I want to keep the second column entry that is associated with it. Best way to explain is through an example.
x = 76 1
36 2
45 3
Now I want to sort x so that it returns an array that looks like:
x = 36 2
45 3
76 1
So the first column has been sorted into numerical order but has retained its second column value. So far I have tried sort(x,1). This sorts the first column as i want but does not keep the pairing. This returns x as:
x = 36 1
45 2
76 3
Any help would be great. Cheers!!
This is exactly what sortrows does.
x=sortrows(x); % or x=sortrows(x,1);
or if you want to use sort then get the sorted indexes first and then arrange the rows accordingly like this:
[~, idx] = sort(x); %Finding the sorted indexes
x = x(idx(:,1),:) ; %Arranging according to the indexes of the first column
Output for both approaches:
x =
36 2
45 3
76 1
I am trying to sort the following one-dimensional array in descending order of values:
109 32 29 22 22 19 15 12 12
I know that in this case, the array is already in descending order but I am trying to figure out why when I use sort(A,'descend'), MATLAB returns a new order:
1 2 3 5 6 4 7 8 9
This is no longer in descending order. This is obviously causing an error in my program whenever the array is in the correct order.
That order you provided is indeed not correct but that is surely not MATLAB's fault. Since your array is already in descending order, the indices of sorting should simply be enumerated from 1 up to 9.
I highly suspect that the culprit is due to you not inputting your array properly. Furthermore, your error can't be reproduced.
This can be verified by putting this into MATLAB and examining the indices of sorting:
A = [109 32 29 22 22 19 15 12 12];
[Ai,ind] = sort(A,'descend');
Ai will be the same as the input A while ind will be enumerated from 1 up to 9 in ascending order.