在Matlab中相交几个不同长度的表格

Question

我在Matlab 中有更多 8 个以上不同长度的表格。它们都在第一列中包含日期。我想在日期列上获得所有这些表的交集。以下带有 3 个表的小示例显示了我想要的内容：

Date1=datenum(2011,6,7,0:24:240,0,0).';
Date2=datenum(2011,6,8,0:24:240,0,0).';
Date3=datenum(2011,6,5,0:24:240,0,0).';


T1 = table(Date1,ones(11,1),'VariableNames',{'Date','Var1'})
T2 = table(Date2,ones(11,1)*2,'VariableNames',{'Date','Var2'})
T3 = table(Date3,ones(11,1)*3,'VariableNames',{'Date','Var3'})

因此，我想要以下输出：

 Date     Var1    Var2    Var3
______    ____    ____    ____

734662    1       2       3   
734663    1       2       3   
734664    1       2       3   
734665    1       2       3   
734666    1       2       3   
734667    1       2       3   
734668    1       2       3   
734669    1       2       3   

Matlab 中有没有可以做到这一点的函数？

Answer 1

intersect 函数可能对您的情况有用。

我不确定您如何使用这些表格，但下面的代码应该可以让您找到每个 DateN 向量的交集索引。一旦你有了索引，你就可以重建一个全局表，它只包含所有表之间的公共索引。

[C,ia,ib ] = intersect(Date1,Date2) ; %// get indices of intersection of first 2 vectors (Date1&2)
[D,ja,ix3] = intersect(  C  ,Date3) ; %// get indices of intersection of last result (Date1&2) with last vector (Date 3)

ix1 = ia(ja) ; %// take only the common indices of the 2 intersection operations (For Date1)
ix2 = ib(ja) ; %// take only the common indices of the 2 intersection operations (For Date2)

%// Build the "common" table
intersectionTable = [ Date1(ix1) Var1(ix1) Var2(ix2) Var3(ix3) ] ;

Answer 2

我为另一个问题写了一个非常相关的代码，我在这里写了一个优美的函数代码，它可以同时找到几个数组的相交元素和相应的索引，而不需要对计算部分使用任何类型的循环.这是代码-

function [out_val,out_idx] = intersect_arrays(varargin)

%// Concatenate all vector arrays into a 2D array
if isrow(varargin{1})
    M = vertcat(varargin{:});
else
    M = horzcat(varargin{:}).';  %//'
end

%// Find unique values for all elements in all arrays
unqvals = unique(M(:),'stable')';  %//'

%// Find unqiue elements common across all arrays (intersecting elements)
out_val = unqvals(all(any(bsxfun(@eq,M,permute(unqvals,[1 3 2])),2),1));

%// Find first indices across all arrays holding the intersecting elements
[~,idx] = max(bsxfun(@eq,M,permute(out_val,[1 3 2])),[],2);
out_idx = squeeze(idx).'; %//'

return

现在，为了解决你的情况，我们可以像这样使用函数代码 -

num_arrays = 3; %// Number of arrays to be used

%// Find intersecting elements and their corresppinding indices in each array
[int_ele,int_idx] = intersect_arrays(T1.Date,T2.Date,T3.Date) %// Add inputs here

%// Create an array of all Var data
all_idx = cat(2,T1.Var1,T2.Var2,T3.Var3)                      %// Add inputs here

%// Select Var data based on the intersecting indices
select_idx = all_idx(bsxfun(@plus,int_idx,[0:num_arrays-1]*size(T1.Var1,1)))

%// Output results as a numeric array and table
out_array = [int_ele(:) select_idx]
out_table = cell2table(num2cell(out_array),'VariableNames',...
                                        {'Date','Var1','Var2','Var3'})

输出 -

out_table = 
     Date     Var1    Var2    Var3
    ______    ____    ____    ____
    734662    1       2       3   
    734663    1       2       3   
    734664    1       2       3   
    734665    1       2       3   
    734666    1       2       3   
    734667    1       2       3   
    734668    1       2       3   
    734669    1       2       3