问题
如何用字符串(最常出现的类)和数字列的平均值替换丢失的列值?
数据示例取自:
例如,将 NaN
替换为'Iris-setosa'
我有代码
它仅替换值,但也如何替换字符串。
function dataWithReplaced = replaceNaNWithAvg(data)
dataWithReplaced = [ ];
averagePerCol = table2array(varfun(@nanmean, data(: , 1:4)));
for i = 1:4
dataColumn = table2array(data( : , i));
dataColumn(isnan(dataColumn)) = averagePerCol(1, i);
dataWithReplaced = [dataWithReplaced dataColumn];
end
end
我是 MATlab 的新手,所以很多事情对我来说并不明显。
最佳答案
以下解决方案解决了该问题:
- 将最后一个表列转换为元胞数组(需要元胞数组来保存不同长度的字符串)。
- Remove all NaN elements from cell array (NaN 元素会扰乱下一节)。
- Find most repeated string in cell array .
- 查找 stringColumn 中 NaN 元素的所有索引(我根据上一节使用了
cellfun
)。 - 用最常见的字符串替换找到的索引中的元素。
由于您是 Matlab 新手,我的解决方案对您来说看起来非常复杂(对我来说看起来很复杂)。
可能有一个更简单的解决方案,但我找不到......
请参阅以下代码示例:
%Create data table for the example.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
VarName1 = [4.9; 7.3; 6.7; 7.2; 6.5; 6.4; 6.8; 5.7; 5.8; 6.4; 6.5];
VarName2 = [2.5; 2.9; 2.5; 3.6; 3.2; 2.7; 3.0; 2.5; 2.8; 3.2; 3.0];
VarName3 = [4.5; 6.3; 5.8; 6.1; 5.1; 5.3; 5.5; 5.0; 5.1; 5.3; 5.5];
VarName4 = [1.7; 1.8; 1.8; 2.5; 2.0; 1.9; 2.1; 2.0; 2.4; 2.3; 1.8];
VarName5 = {NaN; 'aa'; 'aa'; 'bbb'; NaN; 'ccc'; 'ccc'; 'ccc'; 'ccc'; 'dddd'; 'dddd'};
data = table(VarName1, VarName2, VarName3, VarName4, VarName5);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Convert last table column to cell array.
stringColumn = table2cell(data(:, 5));
%Remove all NaN elements from cell array
%Reference: https://www.mathworks.com/matlabcentral/newsreader/view_thread/314852
x = stringColumn(cell2mat(cellfun(@ischar,stringColumn,'UniformOutput',0)));
%Find most repeated string in cell array:
%Reference: https://www.mathworks.com/matlabcentral/answers/7973-how-to-find-out-which-item-is-mode-of-cell-array
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
y = unique(x);
n = zeros(length(y), 1);
for iy = 1:length(y)
n(iy) = length(find(strcmp(y{iy}, x)));
end
[~, itemp] = max(n);
commonStr = y(itemp);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Find all indeces of NaN elements in stringColumn.
nanIdx = find(cell2mat(cellfun(@ischar,stringColumn,'UniformOutput',0)) == 0);
%Rplace elements with NaN values with commonStr.
stringColumn(nanIdx) = commonStr;
%Replace last column of original table
data(:, 5) = stringColumn;
关于MATLAB。用平均值替换缺失值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/40073655/