问题描述
在茎图上，如何添加具有相同x值但具有不同y值的点?
On a stem plot, how can I add points that have the same values of x but different values of y?
例如，给出以下代码:
x = [1 2 3 6 6 4 5];
y = [3 6 1 8 9 4 2];
stem(x,y);
如果绘制x和y，则将是输出:
If you plot x, and y, this will be the output:
我想将(6,8)和(6,9)加起来，使其变成(6,17)，就像图像显示的一样.
I want to add up (6,8) and (6,9) so it becomes (6,17), just like what the image is showing.
我该如何实现?
推荐答案
使用 accumarray 和x和y，因此您可以将共享同一x的类似条目合并或分组.对这些值进行分箱后，您可以将共享同一分箱的所有值相加.这样，我们看到对于x = 6，我们有y = 8和y = 9. accumarray允许您将共享同一x的多个y值组合在一起.将这些值分组之后，您便可以对同一组中的所有值应用函数，以为每个组产生最终输出.在我们的例子中，我们想对它们求和，因此我们需要使用sum函数:
Use accumarray with x and y so you can bin or group like entries together that share the same x. Once these values are binned, you can sum all of the values that share the same bin together. As such, we see that for x = 6, we have y = 8 and y = 9. accumarray allows you to group multiple y values together that share the same x. Once these values are grouped, you then apply a function to all of the values in the same group to produce a final output for each group. In our case, we want to sum them, so we need to use the sum function:
x = [1 2 3 6 6 4 5];
y = [3 6 1 8 9 4 2];
Z = accumarray(x(:), y(:), [], @sum);
stem(unique(x), Z);
xlim([0 7]);
我们在X上使用 unique 在绘制stem图时，我们没有对X的重复. unique还具有排序您的x值的行为.进行x(:)和y(:)是为了使您可以独立地将输入数据作为行向量或列向量. accumarray仅接受列向量(或矩阵，但我们不会去那里)，因此x(:)和y(:)进行操作可确保两个输入均为列向量.
We use unique on X so that we have no repeats for X when plotting the stem plot. unique also has the behaviour of sorting your x values. Doing x(:) and y(:) is so that you can make your input data either as row or column vectors independently. accumarray accepts only column vectors (or matrices, but we won't go there) and so doing x(:) and y(:) ensures that both inputs are column vectors.
我们得到:
上面的代码假定x为整数，并从1开始.如果不是，则使用unique的第三项输出为每个数字分配一个唯一的ID，然后运行通过accumarray.完成后，像往常一样使用accumarray的输出:
The above code assumes that x is integer and starting at 1. If it isn't, then use the third output of unique to assign each number a unique ID, then run this through accumarray. When you're done, use the output of accumarray like normal:
[xu,~,id] = unique(x);
Z = accumarray(id, y(:), [], @sum);
stem(xu, Z);
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