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<div>Porque em vez de usar esse tipo escada de classificação você
não usa um tipo suave? Para mim, este último faz mais sentido.
Veja exemplo de como obter isso com a sua 'escada':<br>
<br>
### Tabela da quinta aproximação <br>
### Nível de Fósforo mg/dm3<br>
###Argila% muito baixo Baixo Médio Bom Muito
Bom<br>
###60-100 <2.7(menor e igual) 2.8-5.4 5.5-8
8.1-12 >12<br>
###35-60 <4 4.1-8 8.1-12 12.1-18
>18<br>
###15-35 <6.6 6.7-12 12.1-20
20.1-30 >30<br>
### 0-15 <10 10.1-20 20.1-30
30.1-45 >45<br>
<br>
escada <- function(x, y, x.br, y.br, ...) { <br>
ix <- findInterval(x, x.br, ...)+1<br>
lr <- lapply(1:nrow(y.br), function(j) {<br>
i <- which(ix==j)<br>
list(i=i, r=findInterval(y[i], y.br[j,], ...)+1)<br>
})<br>
i <- sort(unlist(lapply(lr, function(x) x$i)), <br>
index.return=TRUE, method='quick')$ix<br>
unlist(lapply(lr, function(x) x$r))[i]<br>
}<br>
<br>
### exemplo simulado<br>
n <- 30000<br>
x <- 90*runif(n)<br>
y <- runif(n, 0, 100-x)*.7<br>
<br>
cfosf <- rbind(c(10, 20, 30, 45), c(6.6, 12, 20, 30),<br>
c(4, 8, 12, 18), c(2.7, 5.4, 8, 12))<br>
cfosf<br>
res <- escada(x, y, c(15, 35, 60), cfosf)<br>
table(res)<br>
<br>
plot(x, y, col=res, pch=19, las=1, asp=1, cex=0.3, <br>
xlab="Argila", ylab="Fósforo")<br>
abline(v=c(15, 35, 60), col=gray(.7))<br>
for (j in 1:nrow(cfosf))<br>
segments(c(0, 15, 35, 60)[j], cfosf[j,],<br>
c(15, 35, 60, 100)[j], cfosf[j,], lty=3)<br>
legend("topright", c("Muito baixo", "Baixo", "Médio", "Muito
bom"),<br>
pch=19, col=1:5, bty='n', title='Textura')<br>
segments(0,100,100,0, lty=3)<br>
<br>
### usando esses dados simulados<br>
### (ideal e' usar dados reais)<br>
### para obter uma funcao suave <br>
<br>
require(MASS)<br>
aj <- polr(resp ~ x*y, data.frame(resp=factor(res,
ordered=TRUE)))<br>
<br>
prd <- predict(aj)<br>
<br>
plot(x, y, col=unclass(prd), pch=19, las=1, asp=1, cex=0.3, <br>
xlab="Argila", ylab="Fósforo")<br>
legend("topright", c("Muito baixo", "Baixo", "Médio", "Muito
bom"),<br>
pch=19, col=1:5, bty='n', title='Textura')<br>
<br>
### classificando um novo solo (Argila=36, fosforo=19)<br>
### usando a escada:<br>
escada(36, 19, c(15, 35, 60), cfosf)<br>
### suave:<br>
predict(aj, newdata=data.frame(x=36, y=19)) <br>
<br>
<br>
Att.<br>
Elias.<br>
<br>
</div>
<blockquote
cite="mid:5197e8bf836ed_122c283046c2ef@a4-winter11.tmail"
type="cite">
<hr style="border-top: 1px solid #ccc;">
<div>Em 18/05/2013 09:28, <strong>Hélio Gallo Rocha <
<a class="moz-txt-link-abbreviated" href="mailto:heliogallorocha@gmail.com">heliogallorocha@gmail.com</a> ></strong> escreveu:</div>
<div dir="ltr">Bom dia a todos,
<div> </div>
<div>Para recomendar adubação fosfatada é necessário classificar
a quantidade de fósforo da análise em conjunto a textura do
solo.</div>
<div> </div>
<div>
<table style="border-collapse: collapse; width: 311pt;"
border="0" cellpadding="0" cellspacing="0" width="412">
<colgroup><col style="width: 48pt;" width="64"> <col
style="width: 96pt;" width="128"> <col style="width:
38pt;" span="3" width="50"> <col style="width: 53pt;"
width="70"> </colgroup>
<tbody>
<tr style="height: 12.75pt;">
<td style="height: 12.75pt; width: 48pt;" height="17"
width="64"> Tabela da quinta aproximação
<table style="width: 311pt; margin-left: 3pt;
border-collapse: collapse;" border="0"
cellpadding="0" cellspacing="0" width="415">
<tbody>
<tr style="height: 12.75pt;">
<td style="width: 48pt; border: 1pt solid
windowtext; padding: 0cm 3.5pt; height:
12.75pt;" nowrap="nowrap" valign="bottom"
width="64">
<p><span style="font-size: 10pt; font-family:
Arial;"> </span></p>
</td>
<td style="width: 263pt; border-style: solid
solid solid none; border-top-color:
windowtext; border-right-color: windowtext;
border-bottom-color: windowtext;
border-top-width: 1pt; border-right-width:
1pt; border-bottom-width: 1pt; padding: 0cm
3.5pt; height: 12.75pt;" colspan="5"
nowrap="nowrap" valign="bottom" width="351">
<p style="text-align: center;" align="center"><span
style="font-size: 10pt; font-family:
Arial;">Nível de Fósforo mg/dm3</span></p>
</td>
</tr>
<tr style="height: 12.75pt;">
<td style="width: 48pt; border-style: none solid
solid; border-right-color: windowtext;
border-bottom-color: windowtext;
border-left-color: windowtext;
border-right-width: 1pt; border-bottom-width:
1pt; border-left-width: 1pt; padding: 0cm
3.5pt; height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="64">
<p><span style="font-size: 10pt; font-family:
Arial;">Argila%</span></p>
</td>
<td style="width: 97.7pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="130">
<p><span style="font-size: 10pt; font-family:
Arial;">muito baixo</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">Baixo</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">Médio</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">Bom</span></p>
</td>
<td style="width: 52.5pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="70">
<p><span style="font-size: 10pt; font-family:
Arial;">Muito Bom</span></p>
</td>
</tr>
<tr style="height: 12.75pt;">
<td style="width: 48pt; border-style: none solid
solid; border-right-color: windowtext;
border-bottom-color: windowtext;
border-left-color: windowtext;
border-right-width: 1pt; border-bottom-width:
1pt; border-left-width: 1pt; padding: 0cm
3.5pt; height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="64">
<p><span style="font-size: 10pt; font-family:
Arial;">60-100</span></p>
</td>
<td style="width: 97.7pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="130">
<p><span style="font-size: 10pt; font-family:
Arial;"><2.7 (menor e igual)</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">2.8-5.4</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">5.5-8</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">8.1-12</span></p>
</td>
<td style="width: 52.5pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="70">
<p><span style="font-size: 10pt; font-family:
Arial;">>12</span></p>
</td>
</tr>
<tr style="height: 12.75pt;">
<td style="width: 48pt; border-style: none solid
solid; border-right-color: windowtext;
border-bottom-color: windowtext;
border-left-color: windowtext;
border-right-width: 1pt; border-bottom-width:
1pt; border-left-width: 1pt; padding: 0cm
3.5pt; height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="64">
<p><span style="font-size: 10pt; font-family:
Arial;">35-60</span></p>
</td>
<td style="width: 97.7pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="130">
<p><span style="font-size: 10pt; font-family:
Arial;"><4</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">4.1-8</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">8.1-12</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">12.1-18</span></p>
</td>
<td style="width: 52.5pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="70">
<p><span style="font-size: 10pt; font-family:
Arial;">>18</span></p>
</td>
</tr>
<tr style="height: 12.75pt;">
<td style="width: 48pt; border-style: none solid
solid; border-right-color: windowtext;
border-bottom-color: windowtext;
border-left-color: windowtext;
border-right-width: 1pt; border-bottom-width:
1pt; border-left-width: 1pt; padding: 0cm
3.5pt; height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="64">
<p><span style="font-size: 10pt; font-family:
Arial;">15-35</span></p>
</td>
<td style="width: 97.7pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="130">
<p><span style="font-size: 10pt; font-family:
Arial;"><6.6</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">6.7-12</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">12.1-20</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">20.1-30</span></p>
</td>
<td style="width: 52.5pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="70">
<p><span style="font-size: 10pt; font-family:
Arial;">>30</span></p>
</td>
</tr>
<tr style="height: 12.75pt;">
<td style="width: 48pt; border-style: none solid
solid; border-right-color: windowtext;
border-bottom-color: windowtext;
border-left-color: windowtext;
border-right-width: 1pt; border-bottom-width:
1pt; border-left-width: 1pt; padding: 0cm
3.5pt; height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="64">
<p><span style="font-size: 10pt; font-family:
Arial;">0-15</span></p>
</td>
<td style="width: 97.7pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="130">
<p><span style="font-size: 10pt; font-family:
Arial;"><10</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">10.1-20</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">20.1-30</span></p>
</td>
<td style="width: 37.6pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="50">
<p><span style="font-size: 10pt; font-family:
Arial;">30.1-45</span></p>
</td>
<td style="width: 52.5pt; border-style: none
solid solid none; border-bottom-color:
windowtext; border-bottom-width: 1pt;
border-right-color: windowtext;
border-right-width: 1pt; padding: 0cm 3.5pt;
height: 12.75pt;" nowrap="nowrap"
valign="bottom" width="70">
<p><span style="font-size: 10pt; font-family:
Arial;">>45</span></p>
</td>
</tr>
</tbody>
</table>
</td>
<td style="border-left-style: none; width: 263pt;"
colspan="5" width="348"> </td>
</tr>
</tbody>
</table>
</div>
<div>
<div> </div>
<div> </div>
<div>Fiz o seguinte:</div>
<div>
<div>solo=c(1:50) # resultado da
análise do solo</div>
<div>argila=c(60,35,15,0) # teor de argila</div>
<div>p1=c(0,2.7,5.4,8,12) # fósforo com + de 60%
de argila</div>
<div>p2=c(0,4,8,12,18) # fósforo com 35 a
60% de argila</div>
<div>p3=c(0,6.6,12,20,30) # fósforo com 15 a 35%
de argila</div>
<div>p4=c(0,10,20,30,45) # fósforo com < 15%
de argila</div>
<div>res=c("Muito.Baixo","Baixo", "Medio", "Alto",
"Muito.alto")</div>
<div> </div>
<div>Assim se o resultado de P é 3.5 :</div>
<div>60% de arg, seria classificado como Baixo</div>
<div>35% de arg. seria classificado como muito baixo</div>
<div> </div>
<div>andei dando uma olhada na solução do post </div>
<h1 id="post-title" style="font-family:
GillSans,Trebuchet,Calibri,Arial,sans-serif; color:
#333333; font-size: 1.8em; margin: 0.25em 0px 0.8em;">Uso
do ifelse</h1>
<div> </div>
</div>
<div>A saida desta função seria casada com uma recomendação,</div>
<div> </div>
<div>Grato a todos</div>
<div> </div>
-- <br>
Hélio Gallo Rocha<br>
IFSULDEMINAS - Câmpus Muzambinho</div>
</div>
<div> </div>
<br>
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<br>
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</blockquote>
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