Re: [xsl] Filtering Numeric Output with Changing Parameter

[Joerg Heinicke <joerg dot heinicke at gmx dot de>]

Hello Tim,

the stylesheet is relative simple as you can see. You only have to 
process the nodes step by step:

(added a <root> element in in- and output)

<xsl:template match="root">
    <root>
        <xsl:apply-templates select="stock[1]"/>
    </root>
</xsl:template>

<xsl:template match="stock">
    <xsl:variable name="threshold" select="1"/>
    <xsl:copy-of select="."/>
    <xsl:apply-templates select="following-sibling::stock
            [price >= current()/price + $threshold
          or price &lt;= current()/price - $threshold][1]"/>
</xsl:template>

The first stock must be selected. The next stock, that shell be 
selected, is either "price >= current()/price + $threshold" or "price <= 
current()/price - $threshold", again we will only have the first one, 
that fulfills one of both conditions.

I declared $threshold as variable, you can use it hard-coded in the 
expression or as parameter too.

Regards,

Joerg


Tim Lewis wrote:
> I'd like to take a pile of numeric data and filter it down to a smaller
> pile by selecting for output only values that change by more than a
> threshold amount from the beginning value.  If a value gets selected for
>
> output, then the next output value would have to be different from it by
>
> more than the threshold.  For example, say I have a pile of stock price
> data and I want to plot only values that change by more than 1.00.  If
> the first value is 27.50, then I want to look through the data and
> ignore it until I find a price >= 28.50 or <= 26.50.  If I find a price
> of 28.50, then I want to continue my search, but now I am looking for
> prices >= 29.50 or <= 27.50.
>
>
> So given:
>
> <stock>
>    <time>0.0</time>
>    <price>27.50</price>
> </stock>
> <stock>
>    <time>1.0</time>
>    <price>27.75</price>
> </stock>
> <stock>
>    <time>3.0</time>
>    <price>27.20</price>
> </stock>
> <stock>
>    <time>4.0</time>
>    <price>28.50</price>
> </stock>
> <stock>
>    <time>5.0</time>
>    <price>28.25</price>
> </stock>
> <stock>
>    <time>6.0</time>
>    <price>27.75</price>
> </stock>
> <stock>
>    <time>7.0</time>
>    <price>27.80</price>
> </stock>
> <stock>
>    <time>8.0</time>
>    <price>25.50</price>
> </stock>
>
> I want:
>
> <stock>
>    <time>0.0</time>
>    <price>27.50</price>
> </stock>
> <stock>
>    <time>4.0</time>
>    <price>28.50</price>
> </stock>
> <stock>
>    <time>8.0</time>
>    <price>25.50</price>
> </stock>
>
> I understand that I cannot use a for-each loop because the value of my
> comparison "variables" needs to be variable.  I also understand that I
> need to use recursion to do it.  However, I struggle mightily with
> procedural programming, so functional programming and recursion chew me
> up and spit me out.
>
> Any guidance would be appreciated.  An actual named template to get this
> job done would be even more wondeful!
>
> TIA,
>
> Tim Lewis

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