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POCan't use comma inside backtick column name for data.table setkey?
 

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  1. POCan't use comma inside backtick column name for data.table setkey?
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    <p>If I have a column name that needs backticks because it contains a comma, <code>setkey</code> throws an error saying don't use a comma. The error directs me towards <code>?setkey</code> but I don't see anything in the examples there that mentions this. Only work around I can find is to rename the column, <code>setkey</code> and then rename back.</p> <p>Example code:</p> <pre><code>library(data.table) &gt; DT = data.table(`X, in $` = rnorm(10)) &gt; DT X, in $ 1: -1.28475886 2: 0.97789059 3: -0.05023914 4: -0.38133978 5: -0.24949607 6: 0.99213156 7: -0.29310512 8: 0.02840372 9: 0.25294231 10: -0.88955013 &gt; setkey(DT, `X, in $`) Error in setkeyv(x, cols, verbose = verbose) : Don't use comma inside quotes. Please see the examples in help('setkey') </code></pre> <p><strong>Edit: showing a more likely example</strong></p> <p>For me the main reason you would come across this is after using <code>reshape2</code> <code>dcast</code> to take character column values (which will be from an external source, e.g. database) and make them column names.</p> <p>So long as you don't need the "join" behaviour of the key, and just wanted to sort, then you can work around this by copying the table, or by using <code>data.frame</code> instead. For example:</p> <pre><code>library(ggplot2) library(reshape2) DT = data.table(Office = rep(c("Cambridge, UK", "Cambridge, US", "London", "New York"), each = 12), Product = rep(1:12,4), Sales = rnorm(48)^2) DF = dcast(DT, Product~Office) DT = data.table(DF) setkey(DT, 'Cambridge, UK') DT = DT[order(DF$`Cambridge, UK`),] DT </code></pre> <p>produces:</p> <pre><code>&gt; library(ggplot2) &gt; library(reshape2) &gt; &gt; DT = data.table(Office = rep(c("Cambridge, UK", "Cambridge, US", "London", "New York"), each = 12), Product = rep(1:12,4), Sales = rnorm(48)^2) &gt; DF = dcast(DT, Product~Office) Using Sales as value column: use value.var to override. &gt; DT = data.table(DF) &gt; setkey(DT, 'Cambridge, UK') Error in setkeyv(x, cols, verbose = verbose) : Don't use comma inside quotes. Please see the examples in help('setkey') &gt; DT = DT[order(DF$`Cambridge, UK`),] &gt; DT Product Cambridge, UK Cambridge, US London New York 1: 12 0.0009257347 1.7183751269 0.818101229 0.002499808 2: 1 0.0010855828 0.0889560105 0.083778108 1.451149328 3: 2 0.0139649148 0.7385617360 0.221688602 4.771307440 4: 5 0.0520875574 0.3389613574 0.934932759 0.127634044 5: 10 0.0837778446 0.0598955035 0.015930174 0.715849795 6: 9 0.0856246191 1.1303900183 1.555058058 0.367063297 7: 6 0.1608235273 0.7147643550 0.004588596 2.995598768 8: 8 0.4797866129 0.1783997616 0.016459971 0.497328990 9: 4 0.5282546636 1.7011670679 0.016126768 0.024388172 10: 7 0.5655147714 0.1106522938 0.045130643 0.442473457 11: 3 0.8315246051 0.1399159784 5.792956446 1.632060601 12: 11 3.9958208033 0.0005297928 0.003282897 1.635506818 </code></pre>
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    1. This table or related slice is empty.
    1. PTQuestion
    1. USCorone
    1. USCorone
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
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      1. POCan't use comma inside backtick column name for data.table setkey?
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
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      1. POCan't use comma inside backtick column name for data.table setkey?
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
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      1. POCan't use comma inside backtick column name for data.table setkey?
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      1. VTUpMod
    1. COWhy can't you simply use valid names?
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      1. POCan't use comma inside backtick column name for data.table setkey?
      1. USRoland
    2. CO@Roland The column names will automatically be used for the label and legends etc in generated plots and reports. One solution is simply to avoid it and manually set the output string, like one would in python or languages that don't support escaped variable names, but it would be nice not to have to. My understanding was that one was encouraged to use the display name in your data structures, hence the backtick mechanism.
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      1. POCan't use comma inside backtick column name for data.table setkey?
      1. USCorone
    3. CONo, that's not encouraged. Save the output for printing in a separate character vector.
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      1. POCan't use comma inside backtick column name for data.table setkey?
      1. USRoland
 

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