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POR - vectorised conditional replace
 

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  1. POR - vectorised conditional replace
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    <p>Hi I'm trying manipulate a list of numbers and I would like to do so without a for loop, using fast native operation in R. The pseudocode for the manipulation is :</p> <blockquote> <p>By default the starting total is 100 (for every block within zeros) </p> <p>From the first zero to next zero, the moment the cumulative total falls by more than 2% replace all subsequent numbers with zero.</p> <p>Do this far all blocks of numbers within zeros</p> <p>The cumulative sums resets to 100 every time </p> </blockquote> <p>For example if following were my data :</p> <pre><code>d &lt;- c(0,0,0,1,3,4,5,-1,2,3,-5,8,0,0,-2,-3,3,5,0,0,0,-1,-1,-1,-1); </code></pre> <p>Results would be :</p> <pre><code>0 0 0 1 3 4 5 -1 2 3 -5 0 0 0 -2 -3 0 0 0 0 0 -1 -1 -1 0 </code></pre> <p>Currently I have an implementation with a for loop, but since my vector is really long, the performance is terrible.</p> <p>Thanks in advance.</p> <p>Here is a running sample code :</p> <pre><code>d &lt;- c(0,0,0,1,3,4,5,-1,2,3,-5,8,0,0,-2,-3,3,5,0,0,0,-1,-1,-1,-1); ans &lt;- d; running_total &lt;- 100; count &lt;- 1; max &lt;- 100; toggle &lt;- FALSE; processing &lt;- FALSE; for(i in d){ if( i != 0 ){ processing &lt;- TRUE; if(toggle == TRUE){ ans[count] = 0; } else{ running_total = running_total + i; if( running_total &gt; max ){ max = running_total;} else if ( 0.98*max &gt; running_total){ toggle &lt;- TRUE; } } } if( i == 0 &amp;&amp; processing == TRUE ) { running_total = 100; max = 100; toggle &lt;- FALSE; } count &lt;- count + 1; } cat(ans) </code></pre>
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    1. COshow us your for loop and what you've tried so far
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    2. COThank you chase I updated the post with the code. Thanks for the suggestion.
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    3. COThe Reduce function is useful for sequential processing of vectors, but I cannot figure out what you are trying to do. The `max=100` assignment is much higher than any of the numbers in the input vector and the "processing" variable is never initialized, so as far as I can see 'toggle' remains TRUE forever after the first encounter with a non-zero. It might help if some background about the problem were offered.
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