R不能找到函数"bt.matching.find“

Question

我在从托管在Github上的SIT工具箱实现函数bt.matching.find时遇到了一个问题。按照here描述的步骤下载工具箱后，我尝试复制此blog中描述的代码

library(SIT.dates)
library(SIT)
objt <- bt.matching.find(Cl(data), normalize.fn = normalize.mean, dist.fn = 'dist.euclidean', plot=T)

R没有找到该函数，所以我尝试使用空格来访问该函数

objt <- SIT:::bt.matching.find(Cl(data), normalize.fn = normalize.mean, dist.fn = 'dist.euclidean', plot=T)

但这次我得到了一个奇怪的错误，它与函数中的任何参数都没有关系

Error in last(data, n.reference) : could not find function "last"

我使用函数getAnywhere对函数bt.matching.find进行了研究，得到的结果如下

getAnywhere("bt.matching.find")
A single object matching ‘bt.matching.find’ was found
It was found in the following places
  namespace:SIT
with value

function (data, n.query = 90, n.reference = 252 * 10, n.match = 10, 
    normalize.fn = normalize.mean.sd, dist.fn = dist.euclidean, 
    plot = FALSE, plot.dist = FALSE, layout = NULL, main = NULL) 
{
    data = last(data, n.reference)
    reference = coredata(data)
    n = len(reference)
    query = reference[(n - n.query + 1):n]
    reference = reference[1:(n - n.query)]
    main = paste(main, join(format(range(index(data)[(n - n.query + 
        1):n]), "%d%b%Y"), " - "))
    n.query = len(query)
    n.reference = len(reference)
    dist.fn.name = ""
    if (is.character(dist.fn)) {
        dist.fn.name = paste("with", dist.fn)
        dist.fn = get(dist.fn)
    }
    dist = rep(NA, n.reference)
    query.normalized = match.fun(normalize.fn)(query)
    for (i in n.query:n.reference) {
        window = reference[(i - n.query + 1):i]
        window.normalized = match.fun(normalize.fn)(window)
        dist[i] = match.fun(dist.fn)(rbind(query.normalized, 
            window.normalized))
        if (i%%100 == 0) 
            cat(i, "\n")
    }
    min.index = c()
    temp = dist
    temp[temp > mean(dist, na.rm = T)] = NA
    for (i in 1:n.match) {
            if (any(!is.na(temp))) {
            index = which.min(temp)
            min.index[i] = index
            temp[max(0, index - 2 * n.query):min(n.reference, 
                (index + n.query))] = NA
        }
    }
    n.match = len(min.index)
    if (plot) {
        dates = index(data)[1:len(dist)]
        if (is.null(layout)) {
            if (plot.dist) 
                layout(1:2)
            else layout(1)
        }
        par(mar = c(2, 4, 2, 2))
        if (plot.dist) {
            plot(dates, dist, type = "l", col = "gray", main = paste("Top 
Historical Matches for", 
                main, dist.fn.name), ylab = "Distance", xlab = "")
            abline(h = mean(dist, na.rm = T), col = "darkgray", 
                lwd = 2)
            points(dates[min.index], dist[min.index], pch = 22, 
                col = "red", bg = "red")
            text(dates[min.index], dist[min.index], 1:n.match, 
                adj = c(1, 1), col = "black", xpd = TRUE)
        }
        plota(data, type = "l", col = "gray", LeftMargin = 1, 
            main = iif(!plot.dist, paste("Top Historical Matches for", 
                main), NULL))
        plota.lines(last(data, 90), col = "blue")
        for (i in 1:n.match) {
            plota.lines(data[(min.index[i] - n.query + 1):min.index[i]], 
                col = "red")
        }
        text(index4xts(data)[min.index - n.query/2], reference[min.index - 
            n.query/2], 1:n.match, adj = c(1, -1), col = "black", 
            xpd = TRUE)
        plota.legend(paste("Pattern: ", main, ",Match Number"), 
            "blue,red")
    }
    return(list(min.index = min.index, dist = dist[min.index], 
        query = query, reference = reference, dates = index(data), 
        main = main))
}
<bytecode: 0x000000e7e11c8a00>
<environment: namespace:SIT>

我尝试使用backports包调用该函数

library(backports)
.onLoad <- function(libname, pkgname) {
  backports::import(SIT, "bt.matching.find", force = TRUE)
}

但这也不起作用

为什么R不能访问该函数？这可能是因为这个包是在旧版本下构建的吗？

更多信息

环境

sessionInfo()
R version 3.5.3 (2019-03-11)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 8.1 x64 (build 9600)

Answer 1

这个问题在包的开发人员的帮助下得到了解决，对于任何对使用代码感兴趣的人来说，这里是应该进行的调整

library(SIT)
library(quantmod)
tickers = 'SPY'

data = getSymbols(tickers, src = 'yahoo', from = '1950-01-01', auto.assign = F)


obj = SIT:::bt.matching.find(Cl(data), normalize.fn = SIT:::normalize.mean, dist.fn = 'dist.euclidean', plot=T)

matches = SIT:::bt.matching.overlay(obj, plot.index=1:90, plot=T)

layout(1:2)
matches = SIT:::bt.matching.overlay(obj, plot=T, layout=T)
SIT:::bt.matching.overlay.table(obj, matches, plot=T, layout=T)