What Does This Mean: Unable to Find an Inherited Method for Function 'A' for Signature '"B"'

What does this mean: unable to find an inherited method for function ‘A’ for signature ‘ B ’

That is the type of message you will get when attempting to apply an S4 generic function to an object of a class for which no defined S4 method exists (or at least has been attached to the current R session).

Here's an example using the raster package (for spatial raster data), which is chock full of S4 functions.

library(raster)

## raster::rotate() is an S4 function with just one method, for "Raster" class objects
isS4(rotate)
# [1] TRUE
showMethods(rotate)
# Function: rotate (package raster)
# x="Raster"

## Lets see what happens when we pass it an object that's *not* of class "Raster"
x <- 1:10
class(x)
# [1] "integer"
rotate(x)
# Error in (function (classes, fdef, mtable)  : 
#   unable to find an inherited method for function ‘rotate’ for signature ‘"integer"’

Unable to find an inherited method for function ‘select’ for signature ‘ data.frame ’

There's a great package that helps with package conflicts called conflicted.

If you type search() into your console, you'll see an ordered vector of packages called the "search list". When you call select, R searches through this "search path" and matches the first function called select. When you call dplyr::select you're calling it directly from the namespace dplyr, so the function works as expected.

Here's an example using conflicted. We'll load up raster and dplyr, which both have a select function.

library(dplyr)
library(raster)
library(conflicted)

d <- data.frame(a = 1:10, b = 1:10)

Now when we call select, we're prompted with the exact conflict:

> select(d, a)
Error: [conflicted] `select` found in 2 packages.
Either pick the one you want with `::` 
* raster::select
* dplyr::select
Or declare a preference with `conflict_prefer()`
* conflict_prefer("select", "raster")
* conflict_prefer("select", "dplyr")

Unable to find an inherited method for function 'dbClearResult' for signature ' data.frame '

dbClearResult applies to the query object, not to the result of the fetch (which is a dataframe, hence the error message):

query <- dbSendQuery(db_con,...)

result <- dbFetch(query, n = -1)

dbClearResult(query)

dbDisconnect(db_con)

R unable to find an inherited method for function 'itemFrequency' for signature ' data.frame '

I see that you are trying to implement Apriori algorithm.

To find the itemFrequency of the items in your data set

itemFrequency(mydata)
Error in function (classes, fdef, mtable) :
unable to find an inherited method for function "itemFrequency", for signature "data.frame"

Solution:
step1. load the necessary packages and library like arules, arulesViz
step2. Let say you trying to bring votes data and you need to read the data as transactions

votes <- read.transactions("~/Desktop/votes.csv")
if you just write votes you will have a summary of your transactions as follow
votes
transactions in sparse format with
435 transactions (rows) and
342 items (columns)

Now you can easily find the itemFrequency

itemFrequency(votes)
Here is a sample image

itemFrequency(votes)
democrat 245

republican
345

Hope this will help!

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