add the value of column from text file to the value to matrix

Question

RUCHI CHOUDHARY 2019-9-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/480351-add-the-value-of-column-from-text-file-to-the-value-to-matrix

编辑： Walter Roberson 2019-9-14

i create a matrix having userid as a row and itemid as a column ,now i want to add the value of the third column ,in the index value of userid,itemid.Initially fill the matrix by zeros,but now want the value associate with it.

data=load('u.data');
uni_user=unique(data(:,1));
uni_item=unique(data(:,2));
rating_matrix=zeros(length(uni_user(:,1)),length(uni_item(:,1)));

example this is my dataset

196 242 3

186 302 3

22 377 1

196 51 2

now i want a matrix like

5 个评论
显示 3更早的评论隐藏 3更早的评论

RUCHI CHOUDHARY 2019-9-14

u.csv

i think my question in not clear.matrix is not square matrix so how can we sparse().In actual data file i have 973 unique user and 1683 unique item, so 973*1683 size of matrix is create in which total 10000 rows in column 3 of file is present ,which i want to store in matrix at the index loaction of user and item.possible that for loop is requred to store that data.but i don't know how to use that.

Thank you

Walter Roberson 2019-9-14

sparse() does not require square matrices.

>> full(sparse(1:5,[1 2 3 1 2],1))
ans =
   0     0
   1     0
   0     1
   0     0
   1     0

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Walter Roberson 2019-9-14

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/480351-add-the-value-of-column-from-text-file-to-the-value-to-matrix#answer_391886

编辑：Walter Roberson 2019-9-14

data = load('u.data');
[uni_user, ~, uni_user_idx] = unique(data(:,1));
[uni_item, ~, uni_item_idx] = unique(data(:,2));
rating = data(:,3);
rating_matrix = sparse(uni_user_idx, uni_item_idx, rating);

This will have about 0.6% occupancy and so is well suited for a sparse matrix, but if you have particular reason, you can full() to turn it into a 12 megabyte rectangular array.