我正在尝试编写一个函数，它会改变df中的多个列，并为每个重新编码的变量生成一个新列。在这种情况下，我正在运行的突变是从15中减去列中的每个元素。我能够为三列编写以下代码，这有效，但是在将来我想运行20多列这样的内容写出每个新的列名称（就像你在mutate中所做的那样）似乎很麻烦
我似乎不能使用lapply来使用recode或mutate函数来生成新列。
df2 <- mutate(df1, new_col1 = 15-old_col1,
new_col2 = 15 - old_col2, new_col3 = 15 - old_col3)
答案 0 :(得分：1)
lastClick = [];
var killersGifs = {
killerSearches: ["Freddy Krueger", "Jason Voorhees", "Pennywise", "Ghostface", "American Mary", "Chucky", "Bride of Chucky", "The Candyman", "Cujo", "Hannibal", "Leatherface", "Michael Myers", "Norman Bates", "Pinhead"],
buttonLoop: function() {
for (var b = 0; b < killersGifs.killerSearches.length - 1; b++) {
var buttonM = $("<button class='dynGen'>").text(killersGifs.killerSearches[b]).attr("data-index", killersGifs.killerSearches[b]);
$("#buttons").append(buttonM);
}
},
divLoop: function(click) {
var queryURL = "https://api.giphy.com/v1/gifs/search?api_key=B26sstJns2pZuNT5HiJpqS5FV8Su1sDd&q=" + lastClick + "&limit=10"
$.ajax({
url: queryURL,
method: "GET"
}).done(function(response) {
console.log(response.data);
for (var i = 0; i < response.data.length; i++) {
var respData = response.data[i];
var image = respData.images.fixed_height_still.url;
var gif = respData.images.fixed_height.url;
var rating = respData.rating;
var dynDiv = $("<div class='dyn-div'>");
//dynDiv.attr("data-index", i);
var killerImg = $("<img class='still-image'>");
killerImg.attr("src", image);
killerImg.attr("alt", "Serial Killer still frame of gif");
killerImg.attr("data-gif", gif);
killerImg.attr("class", "killerImg");
killerImg.attr("data-index", i);
killerImg.attr("data-img", image);
dynDiv.append("<p> Rating: " + rating + "</p>");
dynDiv.append(killerImg);
$("#append-img-div").prepend($(dynDiv));
};
});
},
userPush: function () {
var userInput = $("input[type='text']").val().trim();
killersGifs.killerSearches.push(userInput);
var buttonU = $("<button class='dynGen'>").text(userInput).attr("data-index", userInput);
$("#buttons").append(buttonU);
console.log(killersGifs.killerSearches);
}
};
killersGifs.buttonLoop();
$("#killer-add-submit").on("click", function(event) {
event.preventDefault();
killersGifs.userPush();
});
$(document).on("click", "button.dynGen", function(event) {
var currentIndex = $(this).attr("data-index");
lastClick.push(currentIndex);
console.log(currentIndex);
event.preventDefault();
$("#append-img-div").empty();
killersGifs.divLoop();
lastClick = [];
});
$(document).on("click", ".killerImg", function(event) {
console.log("test");
//killersGifs.animateGif();
var currentIn = $(this).attr("data-index");
var tempUrl = $(this).attr("data-gif");
var tempUrl2 = $(this).attr("data-img");
console.log(currentIn);
console.log(tempUrl);
if ($(this).attr("src") == tempUrl2) {
$(this).attr("src", tempUrl);
}
else if ($(this).attr("src") == tempUrl) {
$(this).attr("src", tempUrl2);
};
});
解决方案，假设您要改变所有列*（请参阅下面的更灵活版本）。
*正如@ sb0709在评论中提到的那样，data.table也会这样做。
mutate_all给出了：
library( data.table )
df <- data.table( old_col_1 = 20:24,
old_col_2 = 55:49,
old_col_3 = rnorm( 5, 100, 30 ) )
df[ , sub( "old", "new", names( df ) ) := lapply( .SD, function(x) 15-x ) ]
如果要选择少于所有列，则只需要对R> df
old_col_1 old_col_2 old_col_3 new_col_1 new_col_2 new_col_3
1: 20 55 86.29104 -5 -40 -71.29104
2: 21 56 144.21564 -6 -41 -129.21564
3: 22 57 104.84574 -7 -42 -89.84574
4: 23 58 93.18084 -8 -43 -78.18084
5: 24 59 104.96188 -9 -44 -89.96188
向量和names列表进行子集化。例如，仅在第2列和第3列上运行变异：
.SD而是给出了：
df[ , sub( "old", "new", names( df )[2:3] ) := lapply( .SD[,2:3], function(x) 15-x ) ]