error: element number 2 undefined in return list

Question

以下函数生成错误。

function [retval] = select_red(train, test)
% shuffle test/data points
  shuffled_test = test(randperm(size(test, 1)), :);

  clubs     = shuffled_test(shuffled_test(:, 1) == 1, :);
  diamonds  = shuffled_test(shuffled_test(:, 1) == 2, :);
  hearts    = shuffled_test(shuffled_test(:, 1) == 3, :);
  spades    = shuffled_test(shuffled_test(:, 1) == 4, :);

  clubs = clubs(1: floor(size(clubs,1)/2),:);
  spades = spades(1: floor(size(spades,1)/2),:);

  shuffled_test = [clubs ; diamonds ; hearts ; spades];

  shuffled_test = shuffled_test(randperm(size(shuffled_test, 1)), :);

  ercf_indep = bayescls(train, shuffled_test, @pdfindep, 0.25 * ones(1,4), 0.1);
  ercf_dep = bayescls(train, shuffled_test, @pdfdep, 0.25 * ones(1,4), 0.1);
  ercf_parzen = bayescls(train, shuffled_test, @pdfparzen, 0.25 * ones(1,4), 0.1);

  retval = [ercf_indep   ercf_dep   ercf_parzen];
endfunction

用法

>> [errindep  errdep  errparzen] = select_red(train, test)
errindep =

    0.1089181   0.0029240   0.2309942

    error: element number 2 undefined in return list

你能告诉我为什么会生成错误消息吗？

Answer 1

你对糟糕的功能要求太高了。你想要三个输出，它只能提供一个（这是一个包含三个数字的向量）。

如果您希望函数将三个数字生成为单独的输出，请将其声明为
```
[ercf_indep, ercf_dep, ercf_parzen] = select_red(train, test)
```
并删除末尾的 retval = ... 行。

如果不想修改函数，需要调用一个输出：

out = select_red(train, test);

然后将该输出解压缩为三个数字：

ercf_indep_out = out(1)
ercf_dep =  out(2);
ercf_parzen = out(3);

或者可以使用从元胞数组生成的逗号分隔列表来完成解包：

out_cell = num2cell(out);
[ercf_indep_out, ercf_dep, ercf_parzen] = out_cell{:}

error: element number 2 undefined in return list

error: element number 2 undefined in return list

error-handling

matlab

octave