Subtract mean from each table by columns

Question

wbadry 2020-6-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/548124-subtract-mean-from-each-table-by-columns

评论： Image Analyst 2020-6-22

采纳的回答： Image Analyst

在 MATLAB Online 中打开

Hello,

Assume we have the following table

t = array2table([rand(10,1),rand(10,1),rand(10,1)],'VariableNames',{'feat_1', 'feat_2','feat_3'});

t =

10×3 table

feat_1 feat_2 feat_3

________ ________ _________

0.12991 0.60198 0.82582

0.56882 0.26297 0.53834

0.46939 0.65408 0.99613

0.011902 0.68921 0.078176

0.33712 0.74815 0.44268

0.16218 0.45054 0.10665

0.79428 0.083821 0.9619

0.31122 0.22898 0.0046342

0.52853 0.91334 0.77491

0.16565 0.15238 0.8173

I can get the mean and standard deviation for each solumn using

meanArray = mean(table2array(t,1));
stdArray = std(table2array(t,1));

meanArray =

0.3479 0.4785 0.5547

stdArray =

0.2415 0.2836 0.3793

Is there any vector way to caclulate (element - mean / std) on every element in table without loop and keep the table? Thanks

I know normalize could standardize data but I need to make it in code.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

madhan ravi 2020-6-14

Expected output?

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Image Analyst 2020-6-14

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/548124-subtract-mean-from-each-table-by-columns#answer_451176

编辑：Image Analyst 2020-6-14

在 MATLAB Online 中打开

Try this:

t = array2table([rand(10,1),rand(10,1),rand(10,1)],'VariableNames',{'feat_1', 'feat_2','feat_3'})
m = table2array(t);
meanArray = mean(m)
stdArray = std(m)
z = (m - meanArray) ./ stdArray % a matrix
zt = array2table(z, 'VariableNames',{'feat_1', 'feat_2','feat_3'}) % a table

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

wbadry 2020-6-16

Thank you so much.

请先登录，再进行评论。

Answer 2

wbadry 2020-6-22

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/548124-subtract-mean-from-each-table-by-columns#answer_455152

在 MATLAB Online 中打开

Hello,

I came by another solution using bsxfun

Here is a complete example based on my question

% Generate random columns for the example (10 by 3)
t = array2table([rand(10,1),rand(10,1),rand(10,1)],'VariableNames',...
    {'feat_1', 'feat_2','feat_3'});
% Subtract from the mean vector (3 by 1)
t1 = bsxfun(@minus, mean(table2array(t)),table2array(t));
% Divide by stadard deviation vector (3 by 1) using right array division
t2 = bsxfun(@rdivide,t1,std(table2array(t)));
% Create the standardized table
t = array2table(t2,'VariableNames',{'feat_1', 'feat_2','feat_3'});
% Check mean and std of feat_1
feat_1_mu = mean(t.feat_1)
feat_1_sig = std(t.feat_1)

feat_1_mu =

0

feat_1_sig =

1

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Image Analyst 2020-6-22

Yeah, you can do it that way if you want. I always find their *xfun() functions very cryptic and confusing than the regular math symbols. Plus you always have to find or figure out what the operations are. I mean, who would know, off the top of their head, that if you want to divide something you use @rdivide instead of the slash symbol /, or @minus instead of -. And it gets even more confusing for other operations.

请先登录，再进行评论。