如何输入由不匹配矢量组成的矩阵，以使缺失值用零0填充或不填充NaN？
（显然，可以首先创建一个零的矩阵，并且可以逐行添加不匹配的向量，但是如果我想对此进行1行呢？）
示例：
如何输入矩阵，例如：
a = [
1 2 3 4;
1 2 ;
1 ;
];
导致：
a = [
1 2 3 4;
1 2 0 0;
1 0 0 0;
];
或
c = [
1 2 3 4;
1 2 NaN NaN;
1 NaN NaN NaN;
];
不受欢迎的解决方案：
a = zeros(3,4);
a(1,1:4) = [1 2 3 4];
a(2,1:2) = [1 2 ];
a(3,1:1) = [1 ];
答案 0 :(得分：5)
Jos van der Geest在MathWorks文件交换中提交了一个流行且非常好的实用工具 - padcat。
从本质上讲，它会自动化您建议手动执行的操作。但是，它使用一些智能连接和索引技巧来非常有效地创建所述矩阵。
以下是当前版本：
function [M, TF] = padcat(varargin)
% PADCAT - concatenate vectors with different lengths by padding with NaN
%
% M = PADCAT(V1, V2, V3, ..., VN) concatenates the vectors V1 through VN
% into one large matrix. All vectors should have the same orientation,
% that is, they are all row or column vectors. The vectors do not need to
% have the same lengths, and shorter vectors are padded with NaNs.
% The size of M is determined by the length of the longest vector. For
% row vectors, M will be a N-by-MaxL matrix and for column vectors, M
% will be a MaxL-by-N matrix, where MaxL is the length of the longest
% vector.
%
% Examples:
% a = 1:5 ; b = 1:3 ; c = [] ; d = 1:4 ;
% padcat(a,b,c,d) % row vectors
% % -> 1 2 3 4 5
% % 1 2 3 NaN NaN
% % NaN NaN NaN NaN NaN
% % 1 2 3 4 NaN
% CC = {d.' a.' c.' b.' d.'} ;
% padcat(CC{:}) % column vectors
% % 1 1 NaN 1 1
% % 2 2 NaN 2 2
% % 3 3 NaN 3 3
% % 4 4 NaN NaN 4
% % NaN 5 NaN NaN NaN
%
% [M, TF] = PADCAT(..) will also return a logical matrix TF with the same
% size as R having true values for those positions that originate from an
% input vector. This may be useful if any of the vectors contain NaNs.
%
% Example:
% a = 1:3 ; b = [] ; c = [1 NaN] ;
% [M,tf] = padcat(a,b,c)
% % find the original NaN
% [Vev,Pos] = find(tf & isnan(M))
% % -> Vec = 3 , Pos = 2
%
% This second output can also be used to change the padding value into
% something else than NaN.
%
% [M, tf] = padcat(1:3,1,1:4)
% M(~tf) = 99 % change the padding value into 99
%
% Scalars will be concatenated into a single column vector.
%
% See also CAT, RESHAPE, STRVCAT, CHAR, HORZCAT, VERTCAT, ISEMPTY
% NONES, GROUP2CELL (Matlab File Exchange)
% for Matlab 2008 and up (tested in R2015a)
% version 2.2 (feb 2016)
% (c) Jos van der Geest
% email: samelinoa@gmail.com
% History
% 1.0 (feb 2009) created
% 1.1 (feb 2011) improved comments
% 1.2 (oct 2011) added help on changing the padding value into something
% else than NaN
% 2.2 (feb 2016) updated contact info
% Acknowledgements:
% Inspired by padadd.m (feb 2000) Fex ID 209 by Dave Johnson
narginchk(1,Inf) ;
% check the inputs
SZ = cellfun(@size,varargin,'UniformOutput',false) ; % sizes
Ndim = cellfun(@ndims,varargin) ; %
if ~all(Ndim==2)
error([mfilename ':WrongInputDimension'], ...
'Input should be vectors.') ;
end
TF = [] ; % default second output so we do not have to check all the time
% for 2D matrices (including vectors) the size is a 1-by-2 vector
SZ = cat(1,SZ{:}) ;
maxSZ = max(SZ) ; % probable size of the longest vector
% maxSZ equals :
% - [1 1] for all scalars input
% - [X 1] for column vectors
% - [1 X] for all row vectors
% - [X Y] otherwise (so padcat will not work!)
if ~any(maxSZ == 1), % hmm, not all elements are 1-by-N or N-by-1
% 2 options ...
if any(maxSZ==0),
% 1) all inputs are empty
M = [] ;
return
else
% 2) wrong input
% Either not all vectors have the same orientation (row and column
% vectors are being mixed) or an input is a matrix.
error([mfilename ':WrongInputSize'], ...
'Inputs should be all row vectors or all column vectors.') ;
end
end
if nargin == 1,
% single input, nothing to concatenate ..
M = varargin{1} ;
else
% Concatenate row vectors in a row, and column vectors in a column.
dim = (maxSZ(1)==1) + 1 ; % Find out the dimension to work on
X = cat(dim, varargin{:}) ; % make one big list
% we will use linear indexing, which operates along columns. We apply a
% transpose at the end if the input were row vectors.
if maxSZ(dim) == 1,
% if all inputs are scalars, ...
M = X ; % copy the list
elseif all(SZ(:,dim)==SZ(1,dim)),
% all vectors have the same length
M = reshape(X,SZ(1,dim),[]) ;% copy the list and reshape
else
% We do have vectors of different lengths.
% Pre-allocate the final output array as a column oriented array. We
% make it one larger to accommodate the largest vector as well.
M = zeros([maxSZ(dim)+1 nargin]) ;
% where do the fillers begin in each column
M(sub2ind(size(M), SZ(:,dim).'+1, 1:nargin)) = 1 ;
% Fillers should be put in after that position as well, so applying
% cumsum on the columns
% Note that we remove the last row; the largest vector will fill an
% entire column.
M = cumsum(M(1:end-1,:),1) ; % remove last row
% If we need to return position of the non-fillers we will get them
% now. We cannot do it afterwards, since NaNs may be present in the
% inputs.
if nargout>1,
TF = ~M ;
% and make use of this logical array
M(~TF) = NaN ; % put the fillers in
M(TF) = X ; % put the values in
else
M(M==1) = NaN ; % put the fillers in
M(M==0) = X ; % put the values in
end
end
if dim == 2,
% the inputs were row vectors, so transpose
M = M.' ;
TF = TF.' ; % was initialized as empty if not requested
end
end % nargin == 1
if nargout > 1 && isempty(TF),
% in this case, the inputs were all empty, all scalars, or all had the
% same size.
TF = true(size(M)) ;
end
答案 1 :(得分：2)
如果您只有数字（0-9），这是一个简单的解决方案。输入是一个字符列表，用一个空格或逗号分隔新元素，;表示新行：
str = '1,2 3 4;1,2;1;';
arr = strsplit(str,';');
M = char(arr)-'0';
M(M<0) = 0;
M(:,sum(M)==0)=[]
注意，如果您使用R2016b，则split为recommended而不是strsplit
结果：
M =
1 2 3 4
1 2 0 0
1 0 0 0
0 0 0 0
这是一个包含多个数字的数字的版本。这里的元素必须是一个逗号的saparetad：
str = '1,12,300,4;1,23,3;1';
elem = str2num(char(strsplit(str,',')));
arr = char(strsplit(str,';'));
out = [ones(3,1) arr==','];
out(:,sum(out)==0) = [];
out = out.';
out(out==1) = elem;
out = out.'
结果：
out =
1 12 300 4
1 23 3 0
1 0 0 0