title: scale in data.table in r
body: <pre><code>       LC  RC TOEIC eua again  class
     1: 490 390   880  90     0 100818
     2: 495 395   890  90     0 100818
     3: 490 330   820  90     0 100818
     4: 495 460   955  96     0 100818
     5: 495 370   865  91     0 100818
    ---                               
  1021: 470 400   870  61     0 100770
  1022: 260 180   440  48     0 100770
  1023: 345 190   535  39     0 100770
  1024: 450 295   745  65     0 100770
  1025: 395 230   625  79     0 100770
  </code></pre>
  
  <p>This <code>data.table</code> is named "analy" </p>
  
  <p>I want to scale the variables "LC","RC","TOEIC","eua". 
  I can scale as below</p>
  
  <pre><code>analy[,LC:=scale(LC)]
  analy[,RC:=scale(RC)]
  analy[,TOEIC:=scale(TOEIC)]
  analy[,eua:=scale(eua)]
  </code></pre>
  
  <p>but, I want to know how to scale the variables at once.</p>