title: Filtering a Dataset by another Dataset in R
body: <p>The task I am trying to accomplish is essentially filtering one dataset by the entries in another dataset by entries in an "id" column. The data sets I am working with are quite large having 10 of thousands of entries and 30 or so variables. I have made toy datasets to help explain what I want to do.</p>
  
  <p>The first dataset contains a list of entries and each entry has  their own unique accession number(this is the id).</p>
  
  <pre><code>Data1 = data.frame(accession_number = c('a','b','c','d','e','f'), values =c('1','3','4','2','3','12'))
  &gt;Data1
        accession_number values
  1                a      1
  2                b      3
  3                c      4
  4                d      2
  5                e      3
  6                f     12
  </code></pre>
  
  <p>I am only interested in the entries that have the accession number 'c', 'd', and 'e'. (In reality though my list is around 100 unique accession numbers). Next, I created a dataframe with the only the unique accession numbers and no other values.</p>
  
  <pre><code>&gt;SubsetData1
    accession_number
  1                c
  2                d
  3                e
  </code></pre>
  
  <p>The second data set, which i am looking to filter, contains multiple entries some which have the same accession number.</p>
  
  <pre><code>&gt;Data2
     accession_number values  Intensity col4       col6
  1                 a      1 -0.0251304    a -0.4816370
  2                 a      2 -0.4308735    b -1.0335971
  3                 c      3 -1.9001321    c  0.6416735
  4                 c      4  0.1163934    d -0.4489048
  5                 c      5  0.7586820    e  0.5408650
  6                 b      6  0.4294415    f  0.6828412
  7                 b      7 -0.8045201    g  0.6677730
  8                 b      8 -0.9898947    h  0.3948412
  9                 c      9 -0.6004642    i -0.3323932
  10                c     10  1.1367578    j  0.9151915
  11                c     11  0.7084980    k -0.3424039
  12                c     12 -0.9618102    l  0.2386307
  13                c     13  0.2693441    m -1.3861064
  14                d     14  1.6059971    n  1.3801924
  15                e     15  2.4166472    o -1.1806929
  16                e     16 -0.7834619    p  0.1880451
  17                e     17  1.3856535    q -0.7826357
  18                f     18 -0.6660976    r  0.6159731
  19                f     19  0.2089186    s -0.8222399
  20                f     20 -1.5809582    t  1.5567113
  21                f     21  0.3610700    u  0.3264431
  22                f     22  1.2923324    v  0.9636267
  </code></pre>
  
  <p>What im looking to do is compare the subsetted list of the first data set(SubsetData1), with the second dataset (Data2) to create a  filtered dataset that only contains the entries that have the same accession numbers defined in the subsetted list. The filtered dataset should look something like this. </p>
  
  <pre><code>   accession_number values  Intensity col4       col6
  9                 c      9 -0.6004642    i -0.3323932
  10                c     10  1.1367578    j  0.9151915
  11                c     11  0.7084980    k -0.3424039
  12                c     12 -0.9618102    l  0.2386307
  13                c     13  0.2693441    m -1.3861064
  14                d     14  1.6059971    n  1.3801924
  15                e     15  2.4166472    o -1.1806929
  16                e     16 -0.7834619    p  0.1880451
  17                e     17  1.3856535    q -0.7826357
  </code></pre>
  
  <p>I don't know if I need to start making loops in order to tackle this problem, or if there is a simple R command that would help me accomplish this task. Any help is much appreciated.</p>
  
  <p>Thank You</p>