finding the mean and max

1 次查看（过去 30 天）
johnson saldanha
johnson saldanha 2018-11-21
编辑： Andrei Bobrov 2018-11-21
suppose i have a matrix where the first column is x(:,1)=[ 1 1 1 2 2 1 1 3 1 ] and second column is x(:,2)=[ 2 3 2 4 6 9 7 8 9];
i want the output as y(:,1)=[ 1 2 3 ], y(:,2)=[ 9 6 8] and y(:,3)=[5.33 5 8];
the first column should be the values from first column of x reduced to a single value and in ascending order, the second column should be the highest number from the second column of x for a particular value in first input column. for ex. for all the 1's in first column of x should return one max value from the second column of x. the third column should contain the means of the second column of x for a particular value in first column of x. same example as given.

请先登录，再回答此问题。

采纳的回答

Rik
Rik 2018-11-21
编辑：Rik 2018-11-21
The first column you can achieve with unique, the second and third can be done with accumarray.
x=[ 1 1 1 2 2 1 1 3 1 ; 2 3 2 4 6 9 7 8 9]';
[col1,~,ind]=unique(x(:,1));
col2=accumarray(ind,x(:,2),[],@max);
col3=accumarray(ind,x(:,2),[],@mean);
y=[col1 col2 col3]
  3 个评论
显示 1更早的评论
Walter Roberson
Walter Roberson 2018-11-21
the third output of unique gives you information about the original order .
Rik
Rik 2018-11-21
This code produces the output like you describe. As Walter mentions (and as you can read in the doc of unique) the third output of the unique function returns the order so isequal(col1(ind),x(:,1)) returns true (barring any float rounding errors).
This means that this input will also work as intended:
x=[5 1 1 1 2 2 1 1 3 1 5;9 2 3 2 4 6 9 7 8 9 1]';

请先登录，再进行评论。

更多回答（1 个）

Andrei Bobrov
Andrei Bobrov 2018-11-21
编辑：Andrei Bobrov 2018-11-21
EDITED
>> XXX =[ 1 1 1 2 2 1 1 3 1 ; 2 3 2 4 6 9 7 8 9]'
XXX =
1 2
1 3
1 2
2 4
2 6
1 9
1 7
3 8
1 9
>> T = varfun(@(x)[max(x),mean(x)],array2table(XXX),'G',1);
out = T{:,[1,3]}
out =
1 9 5.3333
2 6 5
3 8 8
>>
  2 个评论
johnson saldanha
johnson saldanha 2018-11-21
Error using getVarIndices (line 27)
Unrecognized variable name 'x1'.
Error in table/varfun (line 104)
groupVars = getVarIndices(a,groupVars);
Error in rider_pattern_mod_n (line 241)
T = varfun(@(xc)[max(xc),mean(xc)],array2table(xc),'G','x1');
got this error
Andrei Bobrov
Andrei Bobrov 2018-11-21
编辑：Andrei Bobrov 2018-11-21
I edited my answer, and you read the help about the MATLAB functions.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 NaNs 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by