根据列中的部分字符串匹配选择数据帧行 [英] Selecting data frame rows based on partial string match in a column

问题描述

我想根据一列中字符串的部分匹配情况从数据框中选择行，例如列"x"包含字符串"hsa".使用 sqldf - if ，它具有类似 like 的语法-我会做类似的事情:

I want to select rows from a data frame based on partial match of a string in a column, e.g. column 'x' contains the string "hsa". Using sqldf - if it had a like syntax - I would do something like:

从<>中选择*；其中x喜欢'hsa'.

不幸的是， sqldf 不支持该语法.

Unfortunately, sqldf does not support that syntax.

或类似地:

selectedRows <- df[ , df$x %like% "hsa-"]

当然不起作用.

有人可以帮我吗?

推荐答案

我注意到您在当前方法中提到了一个函数％like％.我不知道这是否是对"data.table"中％like％的引用，但是如果是这样，则可以按如下方式使用它.

I notice that you mention a function %like% in your current approach. I don't know if that's a reference to the %like% from "data.table", but if it is, you can definitely use it as follows.

请注意，该对象不必是 data.table (但还要记住， data.frame s和 data.table s不同):

Note that the object does not have to be a data.table (but also remember that subsetting approaches for data.frames and data.tables are not identical):

library(data.table)
mtcars[rownames(mtcars) %like% "Merc", ]
iris[iris$Species %like% "osa", ]

如果这就是您所拥有的，那么也许您只是混合了行和列的位置来设置数据.

If that is what you had, then perhaps you had just mixed up row and column positions for subsetting data.

如果不想加载程序包，可以尝试使用 grep()搜索您要匹配的字符串.这是 mtcars 数据集的示例，其中我们匹配行名包含"Merc"的所有行:

If you don't want to load a package, you can try using grep() to search for the string you're matching. Here's an example with the mtcars dataset, where we are matching all rows where the row names includes "Merc":

mtcars[grep("Merc", rownames(mtcars)), ]
             mpg cyl  disp  hp drat   wt qsec vs am gear carb
# Merc 240D   24.4   4 146.7  62 3.69 3.19 20.0  1  0    4    2
# Merc 230    22.8   4 140.8  95 3.92 3.15 22.9  1  0    4    2
# Merc 280    19.2   6 167.6 123 3.92 3.44 18.3  1  0    4    4
# Merc 280C   17.8   6 167.6 123 3.92 3.44 18.9  1  0    4    4
# Merc 450SE  16.4   8 275.8 180 3.07 4.07 17.4  0  0    3    3
# Merc 450SL  17.3   8 275.8 180 3.07 3.73 17.6  0  0    3    3
# Merc 450SLC 15.2   8 275.8 180 3.07 3.78 18.0  0  0    3    3

还有另一个示例，使用 iris 数据集搜索字符串 osa :

And, another example, using the iris dataset searching for the string osa:

irisSubset <- iris[grep("osa", iris$Species), ]
head(irisSubset)
#   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
# 1          5.1         3.5          1.4         0.2  setosa
# 2          4.9         3.0          1.4         0.2  setosa
# 3          4.7         3.2          1.3         0.2  setosa
# 4          4.6         3.1          1.5         0.2  setosa
# 5          5.0         3.6          1.4         0.2  setosa
# 6          5.4         3.9          1.7         0.4  setosa

对于您的问题，请尝试:

For your problem try:

selectedRows <- conservedData[grep("hsa-", conservedData$miRNA), ]

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