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  1. PO
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    <p>First : do not ever in your life use that continue construct again. It's of no use. <code>tryCatch()</code> <em>will</em> continue if you defined a handler for an error or a warning. It will use that one instead of the "default" <code>error=function(e) stop(e)</code>. This one will stop your function. If you define a handler (either <code>warning=</code> or <code>error=</code> ), your script will not be stopped, so that continue is not necessary. </p> <p>This said : The correct use of tryCatch in this case would be :</p> <pre><code>for(i in 1:nrow(symbol)){ tryCatch(prices &lt;- getYahooData(symbol$symbol[i], from, to, freq="daily", type="price"), error = function(e){}) } </code></pre> <p>or, if you use it in a script and want to go to the next loop when an error occurs, you can simply use :</p> <pre><code>for(i in 1:nrow(symbol)){ prices &lt;- try(getYahooData(symbol$symbol[i], from, to, freq="daily", type="price"), silent=TRUE) if(inherits(prices,"try-error")) { next } # only true if an error occurs ... # rest of calculations } </code></pre> <p>If you would have used this way of tryCatch or try, you wouldn't have had the problems you report here. </p> <p>Now I could reproduce your case, if I use nonexistent symbols. Your erroneous use of <code>tryCatch()</code> function is causing you trouble. <code>read.table</code> returns an error (<code>Error in file(file, "rt") : cannot open the connection</code>). This is an <strong>error</strong>, not a warning. You get an additional warning saying that a 404 File not found was returned. </p> <p>When a warning is issued together with an error, the handler function for the warning is dealt with first. That's because a warning has to be thrown before the function can be stopped. So it won't handle the error you get, <s>which means that the <code>on.exit(close(file))</code> in <code>read.table()</code> will not to be called. Hence, the connection is not closed correctly and still considered open, although it can't be found anymore by R (showAllConnections() shows nothing).</s> As the error is not dealt with, something goes wrong in the registration of the connections. As the connection couldn't be opened, the <code>on.exit(close(...))</code> will have no effect. <code>showConnections()</code> doesn't show the connection, but somehow R still thinks it's there. Hence, all hell breaks loose and you crash your R.</p> <p><em>thanks for the corrections to @Tommy</em></p> <p>A simple code example to illustrate this :</p> <pre><code>myfun &lt;- function(x){ if(x&gt;1) warning("aWarning") stop("aStop") x } tryCatch(myfun(0.5), warning=function(w)print("warning"), error=function(e) print("stop")) [1] "stop" tryCatch(myfun(1.5), warning=function(w)print("warning"), error=function(e) print("stop")) [1] "warning" </code></pre> <p>In summary :</p> <ul> <li>check the symbols you use. They're probably wrong.</li> <li>do not ever again use a warning handler if you expect errors.</li> </ul> <p>And as an extra: your loop will only return the result of the last call, as you overwrite <code>prices</code> every time you go through the loop, in case you would have used correct symbols.</p> <p>Edit : in case you want to continue the action </p>
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    1. USJoris Meys
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    1. COJoris - this is simply excellent work! If I could I would give +10.
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    2. COI concur! ...but this indicates a huge flaw in the condition system! on.exit code must be guaranteed to ALWAYS be called, otherwise we're all in deep dodo...
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    3. COHmm I spoke too soon. It seems on.exit is, in general, run when a warning occurs and is caught? And btw, if the connection couldn't be opened, it shouldn't need to be closed either...
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