apply

I have a dataframe that may look like this: A B C foo bar foo bar bar foo foo bar I want to look through every element of each row (or every element of each column) and apply the following function to get the subsequent DF: def foo_bar(x): return x.replace('foo', 'wow') A B C wow bar wow bar bar wow wow bar Is there a simple one-liner that can apply a function to each cell? This is a simplistic example so there may be an easier way to execute this specific example other than applying a function, but what I am really asking about is how to apply a function in every cell within a dataframe.

call： 语法： 1 fun.call(thisArg[, arg1[, arg2[, ...]]]) thisArg：fun函数运行时指定的this值，可能的值为： 不传，或者传null，undefined， this指向 window对象 传递另一个函数的函数名fun2，this指向 函数fun2的引用 值为原始值(数字，字符串，布尔值),this会指向该原始值的自动包装对象，如 String、Number、Boolean 传递一个对象，函数中的this指向这个对象； 例如： 1 2 3 4 5 6 function a(){ console.log(this); } function b(){} a.call(b); // function b(){} 经常会看到这种使用情况： 1 2 3 4 5 function list() { // 将arguments转成数组 return Array.prototype.slice.call(arguments); } list(1,2,3); // [1, 2, 3] 为什么能实现这样的功能将arguments转成数组？首先call了之后，this指向了所传进去的arguments。我们可以假设slice方法的内部实现是这样子的：创建一个新数组，然后for循环遍历this，将this[i]一个个地赋值给新数组，最后返回该新数组

If I have the following case class with a private constructor and I can not access the apply-method in the companion object. case class Meter private (m: Int) val m = Meter(10) // constructor Meter in class Meter cannot be accessed... Is there a way to use a case class with a private constructor but keep the generated apply-method in the companion public? I am aware that there is no difference (in my example) between the two options: val m1 = new Meter(10) val m2 = Meter(10) but I want to forbid the first option. -- edit -- Surprisingly the following works (but is not really what i want): val

I am wondering if there is a built-in function in R which applies a function to each element of the matrix (of course, the function should be computed based on matrix indices). The equivalent would be something like this: matrix_apply <- function(m, f) { m2 <- m for (r in seq(nrow(m2))) for (c in seq(ncol(m2))) m2[[r, c]] <- f(r, c) return(m2) } If there is no such built-in function, what is the best way to initialize a matrix to contain values obtained by computing an arbitrary function which has matrix indices as parameters? I suspect you want outer : > mat <- matrix(NA, nrow=5, ncol=3) >

1、关于call()和apply()的疑点： apply和call的区别在哪里 什么情况下用apply,什么情况下用call apply的其他巧妙用法（一般在什么情况下可以使用apply） 2、语法和参数分析： apply和call都能继承另外一个对象的方法和属性； Function.apply(obj,args)方法能接收两个参数 obj：这个对象将代替Function类里this对象 args：这个是数组，它将作为参数传给Function（args-->arguments） call:和apply的意思一样,只不过是参数列表不一样. Function.call(obj,[param1[,param2[,…[,paramN]]]]) obj：这个对象将代替Function类里this对象 params：这个是一个参数列表 3、call()和apply()示例展示： /*定义一个Person类*/ function Person(name,age) { this.name=name; this.age=age; } /*定义一个学生类*/ function Student(name,age,grade) { //Person.apply(this,arguments);//特点：this指代student对象，只接收2个参数，arguments为隐式类数组对象，用来接收传入的参数；

this是js的一个关键字，随着函数使用场合不同，this的值会发生变化。但是总有一个原则，那就是this指的是调用函数的那个对象。 1、纯粹函数调用。 function test() { this.x = 1; alert(x);}test(); 其实这里的this就是全局变量。看下面的例子就能很好的理解其实this就是全局对象Global。 var x = 1;function test() { alert(this.x);}test();//1var x = 1;function test() { this.x = 0;}test();alert(x);//0 2、作为方法调用，那么this就是指这个上级对象。 function test() { alert(this.x);}var o = {};o.x = 1;o.m = test;o.m(); //1 3、作为构造函数调用。所谓构造函数，就是生成一个新的对象。这时，这个this就是指这个对象。 function test() { this.x = 1;}var o = new test();alert(o.x);//1 4、apply调用 this指向的是apply中的第一个参数。 var x = 0;function test() { alert(this.x);}var o = {};o.x = 1;o.m =

I started to study Scheme and I do not understand some of it. I'm using DrRacket. I wrote the following code: (define mult_mat (λ (A B) (Trans_Mat (map (λ (x) (mul_Mat_vec A x)) (Trans_Mat B))))) That uses this functions: (define Trans_Mat (λ (A) (apply map (cons list A)))) (define mul_Mat_vec (λ (A v) (map (λ (x) (apply + (map * x v))) A))) In mult_mat , I multiply the matrix A in each vector of the transpose matrix B. It works fine. I found a code on the web that makes the multiplication in a way that I don't understand: (define (matrix-multiply matrix1 matrix2) (map (λ (row) (apply map (λ

I'm trying to perform count of an indicator on several (actually hundreds) groups separately (NOT on all combinations of all groups). I'll demonstrate it by simplified example: Assume I have that dataset data<-cbind(c(1,1,1,2,2,2) ,c(1,1,2,2,2,3) ,c(3,2,1,2,2,3)) > data [,1] [,2] [,3] [1,] 1 1 3 [2,] 1 1 2 [3,] 1 2 1 [4,] 2 2 2 [5,] 2 2 2 [6,] 2 3 3 and an indicator some_indicator<-c(1,0,0,1,0,1) then I want to run without loops (like apply by column) something like, aggregate(some_indicator,list(data[,1]),sum) aggregate(some_indicator,list(data[,2]),sum) aggregate(some_indicator,list(data[,3]