在矩阵matlab中查找条件值

时间:2017-08-10 11:48:56

标签: matlab matrix

我有一个矩阵,其中第一列中有家庭ID的个人和第二列中的年龄:

1  32
1  36
1  8
2  50
2  55
3  45
3  40
3  4
3  5
4  23

我想要做的是找出具有特定家庭ID的某些年龄组之间的人数。下面是一些年龄组的例子:

0
1-2
3
4-6 
7-10
etc

因此,如果我搜索家庭ID 1,我想在7-10级中找到1,在寻找家庭ID 3时,我想在课堂上找到2 4-6。我怎么能这样做?

2 个答案:

答案 0 :(得分:1)

histcounts计算直方图,你可以输入edges(边是每个bin的限制);

如何使用您的数据和随机范围在2行中完成此操作的完整示例。您唯一需要知道的是,无论何时您想要一个数字作为bin,您只需将bin的边缘非常接近于值本身。在你的情况下,它们是整数,所以-0.1 +0.1就足够了。

M=[1  32
1  36
1  8
2  50
2  55
3  45
3  40
3  4
3  5
4  23];
ranges=[-0.1 0.1 1 4 20 30 40]; % random
% separate the matrix into cells with unique IDs
Mcell = arrayfun(@(x) M(M(:,1) == x, :), unique(M(:,1)), 'uniformoutput', false);
% Count bins in each cell
result=cellfun(@(x)(histcounts(x(:,2),ranges)),Mcell,'uniformoutput',false)

答案 1 :(得分:1)

您正在寻找的肯定是直方图。但是,我无法在MATLAB中找到支持零宽度分档的内置函数。因此,我写了一个关于如何手动计算所需直方图的小脚本:

% the age data
% (first column: id
% second column: age)
mat_data = [1  32
1  36
1  8
2  50
2  55
3  45
3  40
3  4
3  5
4  23];

% the age classes
% (one class per row,
% lower bound in first column,
% upper bound in second column)
age_classes = [0, 0; ...
               1, 2; ...
               3, 3; ...
               4, 6; ...
               7, 10];

% determine all ids
ids = unique(mat_data(:, 1));

% initialize the output matrix
mat_counts = zeros(size(age_classes, 1), length(ids));

% count the number of entries for each id and age class
for idx_id = 1 : length(ids)
    cur_data = mat_data(mat_data(:, 1) == ids(idx_id), 2);
    for idx_age_class = 1 : length(age_classes)
        cur_age_class = age_classes(idx_age_class, :);
        mat_counts(idx_age_class, idx_id) = length(find(cur_data >= cur_age_class(1) & cur_data <= cur_age_class(2)));
    end
end

% plot everything

% create the x-axis labels
xticks = {};
for idx_age_class = 1 : length(age_classes)
    if length(unique(age_classes(idx_age_class, :))) == 1
        xticks{idx_age_class} = num2str(age_classes(idx_age_class, 1));
    else
        xticks{idx_age_class} = sprintf('%.0f-%.0f', age_classes(idx_age_class, 1), age_classes(idx_age_class, 2));
    end
end

figure(1);
bar(mat_counts);
set(gca, 'xticklabel', xticks);
legend(cellfun(@num2str, num2cell(ids)))
xlabel('age class')
ylabel('count')

这会解决您的问题吗?