Function

function (download_folder, sheet = 2) 
{
    lapply(c("XLConnect", "Nippon"), require, character.only = T)
    path_to_folder <- paste0("C:/Users/", Sys.info()["user"], download_folder)
    setwd(path_to_folder)
    xls_files <- dir()
    sheet_name0 <- XLConnect::getSheets(XLConnect::loadWorkbook(xls_files))
    buf0 <- readWorksheetFromFile(xls_files, sheet = sheet, check.names = F, header = F)
    if (sheet == 2) {
        unittxt <- zen2han(buf0[2, 13])
        datapart0 <- as.numeric(buf0[, 1]) %>% is.na %>% `!` %>% which %>% buf0[., ]
        datapart0[, 1] <- seq(from = as.Date(paste0(datapart0[1, 1], "-1-1")), by = "+1 year", length.out = nrow(datapart0))
        patterntxt <- "△"
        datapart0[, -1] <- apply(datapart0[, -1], 2, function(x) (as.numeric(gsub("\\s|[0-9]+\\)|\\*", "", gsub(patterntxt, "-", x)))))
        namepart0 <- as.numeric(buf0[, 1]) %>% is.na %>% `!` %>% which %>% head(1) %>% seq(from = 1, to = .) %>% buf0[., ] %>% head(., -1)
        colnametxt <- gsub("\\s|NA|[0-9]\\)|\\(再.*掲\\)", "", sapply(paste0(namepart0[3, ], namepart0[4, ], namepart0[5, ], namepart0[6, ]), zen2han))
        colnames(datapart0) <- colnametxt
        datadf <- datapart0[, colnames(datapart0) != ""]
        datadf <- datadf[, -tail(grep("年次", colnames(datadf)), 1)]
        rownames(datadf) <- NULL
    }
    return(list(datadf = datadf, unittxt = unittxt))
}