How to find the highest value of a column in a data frame in R

Question

I have the following data frame which I called ozone      Ozone Solar R Wind Temp Month Day 1     41     190  7 4   67     5   1 2     36     118  8 0   72     5   2 3     12     149 12 6   74     5   3 4     18     313 11 5   62     5   4 5     NA      NA 14 3   56     5   5 6     28      NA 14 9   66     5   6 7     23     299  8 6   65     5   7 8     19      99 13 8   59     5   8 9      8      19 20 1   61     5   9   I would like to extract the highest value from ozone  Solar R  Wind     Also  if possible how would I sort Solar R or any column of this data frame in descending order  I tried   max ozone  na rm T    which gives me the highest value in the dataset   I have also tried   max subset ozone Ozone     but got  subset  must be logical    I can set an object to hold the subset of each column  by the following commands  ozone  lt - subset ozone  Ozone  gt 0  max ozone na rm T     but it gives the same value of 334  which is the max value of the data frame  not the column   Any help would be great  thanks

User · Answer

To get the max of any column you want something like:

max(ozone$Ozone, na.rm = TRUE)

To get the max of all columns, you want:

apply(ozone, 2, function(x) max(x, na.rm = TRUE))

And to sort:

ozone[order(ozone$Solar.R),]

Or to sort the other direction:

ozone[rev(order(ozone$Solar.R)),]

User · Answer

There is a package matrixStats that provides some functions to do column and row summaries  see in the package vignette  but you have to convert your data frame into a matrix   Then you run  colMaxs as matrix ozone

User · Answer

Try this solution    Oz lt -subset data  data Month  5 select Ozone    select ozone  value in the month of                                                                May  i e  Month   5  summary T                                     gives caracteristics of table  contains 1 column of Ozone  including max  min

User · Answer

max may Ozone  na rm   TRUE    Without  Ozone it will filter in the whole data frame  this can be learned in the swirl library   I m studying this course on Coursera too

User · Answer

max ozone Ozone  na rm   TRUE  should do the trick  Remember to include the na rm   TRUE or else R will return NA

User · Answer

In response to finding the max value for each column  you could try using the apply   function    gt  apply ozone  MARGIN   2  function x  max x  na rm TRUE     Ozone Solar R    Wind    Temp   Month     Day     41 0   313 0    20 1    74 0     5 0     9 0

User · Answer

Here s a dplyr solution   library dplyr     find max for each column summarise each ozone  funs max    na rm TRUE       sort by Solar R  descending arrange ozone  desc Solar R     UPDATE  summarise each   has been deprecated in favour of a more featureful family of functions  mutate all    mutate at    mutate if    summarise all    summarise at    summarise if    Here is how you could do     find max for each column ozone   gt            summarise if is numeric  funs max    na rm TRUE     gt            arrange Ozone    or   ozone   gt            summarise at vars 1 6   funs max    na rm TRUE     gt            arrange Ozone

User · Answer

Assuming that your data in data frame called maxinozone  you can do this  max maxinozone 1     na rm   TRUE

User · Answer

Another way would be to use  pmax  do call  pmax   c as data frame t ozone   na rm TRUE     1   41 0 313 0  20 1  74 0   5 0   9 0

User · Answer

Similar to colMeans  colSums  etc  you could write a column maximum function  colMax  and a column sort function  colSort     colMax  lt - function data  sapply data  max  na rm   TRUE  colSort  lt - function data       sapply data  sort         I use     in the second function in hopes of sparking your intrigue   Get your data   dat  lt - read table h T  text    Ozone Solar R Wind Temp Month Day 1     41     190  7 4   67     5   1 2     36     118  8 0   72     5   2 3     12     149 12 6   74     5   3 4     18     313 11 5   62     5   4 5     NA      NA 14 3   56     5   5 6     28      NA 14 9   66     5   6 7     23     299  8 6   65     5   7 8     19      99 13 8   59     5   8 9      8      19 20 1   61     5   9     Use colMax function on sample data   colMax dat     Ozone Solar R    Wind    Temp   Month     Day      41 0   313 0    20 1    74 0     5 0     9 0   To do the sorting on a single column    sort dat Solar R  decreasing   TRUE     1  313 299 190 149 118  99  19   and over all columns use our colSort function    colSort dat  decreasing   TRUE     compare with       above

[r] How to find the highest value of a column in a data frame in R?

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