按行名和列名访问矩阵，如果不可用，则返回零 [英] access matrix by rownames and colnames, and return zero if not available

问题描述

我有一个矩阵，其行名和列名分别为:

I have a matrix with rownames and colnames as:

a = matrix(1:4,2,2)
dimnames(a) = list(c("x","y"),c("x","y"))

例如，我可以按行名和列名访问矩阵元素

I can have access to matrix elements by rownames and colnames, for example,

a["x","y"]

当我键入a ["x"，"z"]时，它给我一个错误"a [" x，" z]中的错误:下标超出范围"，应该是.

When I type a["x","z"], it gives me an error "Error in a["x", "z"] : subscript out of bounds", which should be.

我的问题是我怎么能得到零而不是那个错误.更确切地说，当我键入错误的行名或不在行名(a)或colnames(a)中的列名时，它将返回一个固定值，例如零.例如，对于a ["x"，"z"]，a ["z"，"t"]，...，为零.

My question is how can I get zero instead of that error. More precisely, when I type wrong rownames or colnames that are not in rownames(a) or colnames(a), it returns a fixed value such as zero. For example, zero for a["x","z"], a["z","t"], ... .

推荐答案

将其包装在tryCatch中.不使用任何软件包:

Wrap it in tryCatch. No packages are used:

tryCatch(a["x", "y"], error = function(e) 0)
## [1] 3

tryCatch(a["x", "w"], error = function(e) 0)
## [1] 0

这篇关于按行名和列名访问矩阵，如果不可用，则返回零的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！