blocks|key|3824255|text|下面是一种典型的拆分/应用/组合方法。但是，您应该知道，通过在数字列中引入字符串，整个列将转换为字符。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3824256|do.call(rbind,+lapply(split(is,+is$cast),+transform,+depth+=+
+ifelse(depth+==+min(depth),+"surface",+ifelse(depth+==+max(depth),+"bottom",+depth))))
#++++cast+++depth
#a.1++++a+surface
#a.2++++a++++++20
#a.3++++a++bottom
#b.4++++b+surface
#b.5++++b++++++15
#b.6++++b++bottom|code-block|syntax|javascript|3824257|为了避免类型转换，可以考虑一种不同的方法，例如：|3824258|do.call(rbind,+lapply(split(is,+is$cast),+transform,+
+++++++++++++surface+=+depth+==+min(depth),+
+++++++++++++bottom++=+depth+==+max(depth)))
#++++cast+depth+surface+bottom
#a.1++++a++++10++++TRUE++FALSE
#a.2++++a++++20+++FALSE++FALSE
#a.3++++a++++30+++FALSE+++TRUE
#b.4++++b+++++5++++TRUE++FALSE
#b.5++++b++++15+++FALSE++FALSE
#b.6++++b++++25+++FALSE+++TRUE|3824259|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Here's a classic split/apply/combine approach. However, you should be aware that by introducing strings in a numeric column, the whole column will be converted to character.

<pre><code>do.call(rbind, lapply(split(is, is$cast), transform, depth = 
 ifelse(depth == min(depth), "surface", ifelse(depth == max(depth), "bottom", depth))))
# cast depth
#a.1 a surface
#a.2 a 20
#a.3 a bottom
#b.4 b surface
#b.5 b 15
#b.6 b bottom
</code></pre>

To avoid type conversion you could consider a different approach, for example:

<pre><code>do.call(rbind, lapply(split(is, is$cast), transform, 
 surface = depth == min(depth), 
 bottom = depth == max(depth)))
# cast depth surface bottom
#a.1 a 10 TRUE FALSE
#a.2 a 20 FALSE FALSE
#a.3 a 30 FALSE TRUE
#b.4 b 5 TRUE FALSE
#b.5 b 15 FALSE FALSE
#b.6 b 25 FALSE TRUE
</code></pre>

blocks|key|796593|text|如果每个“强制转换”只有一个最小/最大值，则另一个选项是使用data.table。将“data.frame”转换为“data.table”(setDT(is))，按“强制”分组，我们将“深度”组合成“深度”，并将“面”连接到“深度”的元素(最后一个除外)，然后是‘底部’，从而创建新的列。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|796594|+library(data.table)
+setDT(is)[order(depth),+depth1+:=+c('surface',
++++++++++++++++++++++++depth[2:(.N-1)],+'bottom')+,cast]
+is
+#++cast+depth++depth1
+#1:++++a++++10+surface
+#2:++++a++++20++++++20
+#3:++++a++++30++bottom
+#4:++++b+++++5+surface
+#5:++++b++++15++++++15
+#6:++++b++++25++bottom|code-block|syntax|javascript|796595|如果有的情况下，只有一个观察‘演员’|796596|+setDT(is)[order(depth),+depth1+:=+if(.N+>+1)+
++++c('surface',+depth[2:(.N-1)],+'bottom')+else+depth+,cast]|796597|entityMap^0|U|A|1Y|9|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

If there is only one minimum/maximum value per 'cast', another option is using <code>data.table</code>. Convert the 'data.frame' to 'data.table' (<code>setDT(is)</code>), grouped by 'cast', we <code>order</code> the 'depth', and create the new column by concatenating 'surface' to the elements of 'depth' except the last one, followed by 'bottom'. 

<pre><code> library(data.table)
 setDT(is)[order(depth), depth1 := c('surface',
 depth[2:(.N-1)], 'bottom') ,cast]
 is
 # cast depth depth1
 #1: a 10 surface
 #2: a 20 20
 #3: a 30 bottom
 #4: b 5 surface
 #5: b 15 15
 #6: b 25 bottom
</code></pre>

If there are cases where there is only a single observation for 'cast' 

<pre><code> setDT(is)[order(depth), depth1 := if(.N &gt; 1) 
 c('surface', depth[2:(.N-1)], 'bottom') else depth ,cast]
</code></pre>

blocks|key|3909770|text|使用by的类似方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3909771|#+First+cbind+an+index
is$index+<-+1:nrow(is)

#+then+find+the+max+and+min+and+return+the+indeces
foo+<-+function(x)+cbind(min=+x$index[which.min(x$depth)],+max=+x$index[which.max(x$depth)])
gr+<-+do.call(rbind,+by(is,+list(is$cast),+FUN=++foo))

#+subset+the+extremes+and+replace+the+values+with+your+choice.+
is[gr[,1],+"depth"]+<-+"surface"
is[gr[,2],+"depth"]+<-+"bottom"|code-block|syntax|javascript|3909772|entityMap^0|2|2|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

A similar approach using <code>by</code>. 

<pre><code># First cbind an index
is$index &lt;- 1:nrow(is)

# then find the max and min and return the indeces
foo &lt;- function(x) cbind(min= x$index[which.min(x$depth)], max= x$index[which.max(x$depth)])
gr &lt;- do.call(rbind, by(is, list(is$cast), FUN= foo))

# subset the extremes and replace the values with your choice. 
is[gr[,1], "depth"] &lt;- "surface"
is[gr[,2], "depth"] &lt;- "bottom"
</code></pre>

blocks|key|794577|text|您也可以使用tapply|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|794578|newdepth+<-+c(is$cast,is$depth)
newdepth[is==tapply(is$depth,is$cast,max)]+<-+"bottom"
newdepth[is==tapply(is$depth,is$cast,min)]+<-+"surface"

want+<-+is
want$depth+<-+newdepth[-(1:nrow(want))]|code-block|syntax|javascript|794579|但请注意want$depth中的字符值，如@docendo弟子所述。|794580|entityMap^0|6|6|0|0|4|A|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

You can also use <code>tapply</code>:

<pre><code>newdepth &lt;- c(is$cast,is$depth)
newdepth[is==tapply(is$depth,is$cast,max)] &lt;- "bottom"
newdepth[is==tapply(is$depth,is$cast,min)] &lt;- "surface"

want &lt;- is
want$depth &lt;- newdepth[-(1:nrow(want))]
</code></pre>

But be aware of character values in <code>want$depth</code> as @docendo discimus stated.

I have a df of oceanographic data with CTD cast/station names in one column and depth in another. It looks something like this

<pre><code>is &lt;- data.frame(cast=c("a","a","a","b","b","b"), depth=c(10,20,30,5,15,25))
</code></pre>

Now I would like to find the min and max depth for each cast and replace the value with "surface" and "bottom", respectively. The result should look like this:

<pre><code>want &lt;- data.frame(cast=c("a","a","a","b","b","b"), depth=c("surface",20,"bottom","surface",15,"bottom"))
</code></pre>

I have used aggregate() to find each min/max and tried ifelse() with for loop to replace the values but couldn't make it work. 
Help is much appreciated.
David

find minima and replace with character string in r

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

我有一个海洋数据的df，CTD转换/站名在一列，深度在另一列。看上去像这样is <- data.frame(cast=c("a","a","a","b","b","b"), depth=c(10,20,30,5,15,25))现在我想找出每个铸体的最小深度和最大深度，并将值分别替换为“表面”和“底部”。结果应该如下所示...

问查找最小值并用r中的字符串替换
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问查找最小值并用r中的字符串替换EN