Sample (random) filter operation

Devin Weaver

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Sep 9, 2019, 4:05:43 PM9/9/19

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For anyone curious here is a neat filter option to grab a random tiddler from a list:

<$list filter="[tag[quote]sample[3]]">
<$transclude/>
</$list>

will show you three random tiddlers with the quote tag.

/*\
title: $:/filters/sample.js
type: application/javascript
module-type: filteroperator

Filter to return random set from the current list.

\*/
(function(){

/*jslint node: true, browser: true */
/*global $tw: false */
"use strict";

/*
Export our filter function
*/
exports.sample = function(source,operator,options) {
  var sampleIndex;
  var allTitles = [];
  var samples = [];
  var numberOfSamples = parseInt(operator.operand) || 1;
  source(function(tiddler,title) { allTitles.push(title); });
  if (numberOfSamples >= allTitles.length) { return allTitles; }
  for (var i = 0; i < numberOfSamples; i++) {
    sampleIndex = Math.floor(Math.random() * allTitles.length);
    samples = samples.concat(allTitles.splice(sampleIndex, 1));
  }
  return samples;
};

})();

TonyM

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Sep 9, 2019, 9:56:49 PM9/9/19

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Devin,

Thanks for sharing. This would be very useful to some. Could you please outline how to install it for use so a broader audience can make use of it.?

Regards

Tony

Mohammad Rahmani

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Sep 10, 2019, 2:51:56 AM9/10/19

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Great share Devin!

It would be nice to add a small instruction for people how like to use your script / filter in their wiki!

Best wishes

Mohammad

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Mohammad Rahmani

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Sep 10, 2019, 1:11:51 PM9/10/19

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One question,

How about the performance effects? It seems when a tiddler uses this filter every change on the screen trigger the simple filter!

Best wishes

Mohammad

On Tue, Sep 10, 2019 at 12:35 AM Devin Weaver <weaver...@gmail.com> wrote:

@TiddlyTweeter

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Sep 10, 2019, 1:21:27 PM9/10/19

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One query. DO we need JavaScript for that?

I thought it was doable in TW already?

TT

On Tuesday, 10 September 2019 19:11:51 UTC+2, Mohammad wrote:

One question,
How about the performance effects? It seems when a tiddler uses this filter every change on the screen trigger the simple filter!

Best wishes
Mohammad

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Mohammad Rahmani

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Sep 10, 2019, 1:41:37 PM9/10/19

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Hi TT

Is there any filter or math operator to do this?

Best wishes

Mohammad

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@TiddlyTweeter

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Sep 10, 2019, 1:53:58 PM9/10/19

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See https://groups.google.com/forum/#!searchin/tiddlywiki/random$20numbers$20josiah%7Csort:date/tiddlywiki/N263pebgCYI/bWkecUA7AwAJ

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Mark S.

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Sep 10, 2019, 2:31:58 PM9/10/19

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That's all based on Tobias' random filter. Looking at the code, it appears nearly identical Devin's. I suppose there's only so many

ways to wrap that functionality.

I guess one slight improvement would be to pass in context that would prevent the number from changing every time the tiddler was refreshed.

Perhaps use the suffix (as if a field) to indicate "this usage here.". So it would be locked in until the browser reloaded.

Note that all random implementations are pseudo random. Supposedly browsers now have an api, window.crypto.getRandomValues, that

produces better random values. I don't know how they can do that -- it's like pulling a rabbit out of thin air. The randomness thing only

matters if you're doing things like encrypting critical data, pulling numbers for a lottery or doing a research study.

@TiddlyTweeter

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Sep 10, 2019, 2:55:42 PM9/10/19

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Ciao Mark et al

I wish we had better ways to improve the wheel other than someones serendipitous memory of times past.

Mark makes interesting points about the refresh process and the underlying api.

TT

Mohammad Rahmani

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Sep 11, 2019, 3:38:55 AM9/11/19

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Which of those solution does not use JS?

Of course I think in 5.1.20+ it is possible to use math operators plus the now macro to create random number

Best wishes

Mohammad

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Mohammad

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Sep 11, 2019, 10:05:20 AM9/11/19

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Thanks Mark!

Yes, in TW actually this is useful when one displays a random tiddler content for example at startup!