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POWriting a function to separate working vs. error values in R
 

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  1. POWriting a function to separate working vs. error values in R
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    <p>I've been using this awesome code from the Heuristic Andrew <a href="http://heuristically.wordpress.com/2013/05/20/geolocate-ip-addresses-in-r/" rel="nofollow">blog</a></p> <p>where you can geolocate IP addresses. I want to be able to run the function over a large (24867 IPs) vector of IP addresses. The problem is most of the IP addresses will return the following error:</p> <pre><code>Error in file(con, "r") : cannot open the connection In addition: Warning message: In file(con, "r") : cannot open: HTTP status was '404 Not Found' </code></pre> <p>I'm assuming this occurs because the IP address can not be traced. </p> <p>I want to create a subset of the vector of IP addresses that will give me the location. I think I would need to write another function puts the IP address into a new vector of working IP addresses, or into a different vector of error IP addresses. </p> <p>I think I would also need to use the <code>try</code> or <code>tryCatch</code> function? </p> <p>I'm new to programming so I don't know how to write a function. I've looked at examples online but can't quite figure it out. Any advice would be appreciated.</p> <p><em><strong>EDIT:</em></strong> Thanks to @Thomas for pointing me down the right road...</p> <p>I used the function is.error to determine if <code>try()</code> will give me an error or not. Returns a logical vector:</p> <pre><code>is.error &lt;- function(x) inherits(x, "try-error") </code></pre> <p>Tried using <code>lapply()</code></p> <pre><code>&gt; is.error( + try( + lapply(X = ls_IPaddresses, FUN = freegeoip) + ) + ) Error in file(con, "r") : cannot open the connection [1] TRUE </code></pre> <p>The length of ls_IPaddresses is 24867, so I would want a logical vector with the same length so I can subset the logical vector against ls_IPaddresses.</p>
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    1. CO`try` should be sufficient here (basically just wrap the `readLines` function in `try` and return `NULL` when `inherits(x, "try-error")`). Take a look at [Hadley's tutorial](https://github.com/hadley/devtools/wiki/Exceptions-Debugging#handling), which has a pretty clear discussion on this.
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    2. COThis is a good starting point... The IP addresses are in a vector, so I want to run the freegeoip() function, and get a logical vector where TRUE means there was an error and FALSE means I can run freegeoip(). When I use the readLines function I get this error: "invalid 'description' argument". Will edit question with codes I used.
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    3. CO@camelarms flodel seems to have given you a good answer along the lines of what I was suggesting.
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