从只有一个值不同的行对中获取唯一行（观察）

Posted 2021-04-06

我有一个data.table，它有许多行，q.val的值不同。对于这些对中的每一对，我想选择具有较小值的行。换句话说，我想从DT1到DT2（见下文）。在data.table包或其他方面有一个简单的方法吗？

DT1
cluster q.val
c1  8.68E-03
c1  1.00E+00
c2  4.53E-05
c2  1.00E+00
c3  2.46E-03
c3  1.00E+00
c4  4.18E-05
c4  1.00E+00
c5  1.00E+00
c5  3.98E-05
c6  1.00E+00
c6  4.71E-06

DT2
cluster q.val
c1  8.68E-03
c2  4.53E-05
c3  2.46E-03
c4  4.18E-05
c5  3.98E-05
c6  4.71E-06

鉴于我通过原始问题编辑的答案，以发布我的真实表格的一部分

cluster pathway q.val
c1  Adrenergic signaling in cardiomyocytes  -3.01E-06
c1  Adrenergic signaling in cardiomyocytes  -1.80E+00
c2  Adrenergic signaling in cardiomyocytes  -5.07E-06
c2  Adrenergic signaling in cardiomyocytes  -1.30E+00
c3  Adrenergic signaling in cardiomyocytes  -1.46E-06
c3  Adrenergic signaling in cardiomyocytes  -2.32E+00
c4  Adrenergic signaling in cardiomyocytes  -1.60E-05
c4  Adrenergic signaling in cardiomyocytes  -1.75E+00
c5  Adrenergic signaling in cardiomyocytes  2.58E+00
c5  Adrenergic signaling in cardiomyocytes  2.53E-06
c6  Adrenergic signaling in cardiomyocytes  3.54E+00
c6  Adrenergic signaling in cardiomyocytes  8.74E-08
c7  Adrenergic signaling in cardiomyocytes  -4.85E-02
c7  Adrenergic signaling in cardiomyocytes  -3.98E-03
c8  Adrenergic signaling in cardiomyocytes  9.73E-01
c8  Adrenergic signaling in cardiomyocytes  3.44E-05
c1  Aldosterone synthesis and secretion -3.01E-06
c1  Aldosterone synthesis and secretion -1.64E+00
c2  Aldosterone synthesis and secretion -5.07E-06
c2  Aldosterone synthesis and secretion -1.49E+00
c3  Aldosterone synthesis and secretion -1.46E-06
c3  Aldosterone synthesis and secretion -1.85E+00
c4  Aldosterone synthesis and secretion -1.60E-05
c4  Aldosterone synthesis and secretion -1.40E+00
c5  Aldosterone synthesis and secretion 2.58E+00
c5  Aldosterone synthesis and secretion 2.53E-06
c6  Aldosterone synthesis and secretion 3.45E+00
c6  Aldosterone synthesis and secretion 8.74E-08
c7  Aldosterone synthesis and secretion -1.28E-02
c7  Aldosterone synthesis and secretion -1.42E-02
c8  Aldosterone synthesis and secretion 4.24E-01
c8  Aldosterone synthesis and secretion 3.44E-05

答案

DT1[, min(q.val), by = c("cluster", "pathway")]

data.table中的基本语法允许您使用“by”语句来区分应用函数（在本例中为“min”）的位置。值得注意的是，只有每个群集没有多个不同的路径时，这才有效。如果有，则每个群集将有多个行。