R help - May 2010 - How to find all single minima, i.e. only each one within each next part of analyzed vector (table)

Dear R users,
How to find all single minima within each next part of analyzed vector (table)
Select all minima (mass_value=min & mass_value<2) 
(many) in vector(table), 
BUT first put mask on table in order to select 
within one window mask (5 elements) only one local minimum, and next to search
within
the next time window mask the second minimum (only one local along second mask)
 
mass_position<-c(1,2,3,4,5,6,7,8,9,10, 11,12,13,14,15,16,17,18,19,20)
mass_value<-c(9,2,3,2,5,6,7,8,9,10,2.1,12, 1,14,15,16,17,18,19,20)
mass_label<-c("lab1","lab2","lab3","lab4","lab5","lab6","lab7","lab8","lab9","lab10",
      
"lab11","lab12","lab13","lab14","lab15","lab16","lab17","lab18","lab19","lab20")

dt<-5

# i.e.
 mass_value<-c   (9,0,3,1,5,6,7,8,3,10,2.1,12, 1, 1,15,16,17,18,19,20)
 mass_position<-c(1,2,3,4,5,6,7,8,9,10, 11,12,13,14,15,16,17,18,19,20)
#                 - - - - -                                       
#                   1   x                                      first needed min=
0, pos=2
#(only one within first mask)          
#                           - - - x  -                            
#                           (min= 3, but & ( 3 is not <2)) =>there is
not min for us locally

#                                        -  -  -  -  -
#                                              1  x             2nd needed  
min=1,pos=13
# not min=1 on position 14, because we want only 1 min locally 
#  and only one locally within each NEXT 5 elements)
#
#                                                      .  .  .  .  . 

#correct answer would be vector :
# "lab2","lab13" 

#expected answer = 
local_min_positions = (2     ,13     ) 
local_min_values    = (0     ,1      )
local_min_labels    = ("lab2","lab13")

How to find labels from my_label:
for all localizations of different minima in mass, 
but within time window there can be only one minimum, 
i.e. in dt=5 second wide time window there can be only one minimum

Yours sincerely,
Eugen



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I hope this will help.

### Find rows with minimum value from every 5 rows
## Create the data
mlb <- data.frame(mass_position=c(1,2,3,4,5,6,7,8,9,10,
11,12,13,14,15,16,17,18,19,20),
	mass_value=c(9,2,3,2,5,6,7,8,9,10,2.1,12, 1,14,15,16,17,18,19,20),

mass_label=c("lab1","lab2","lab3","lab4","lab5","lab6","lab7","lab8","lab9","lab10",

"lab11","lab12","lab13","lab14","lab15","lab16","lab17","lab18","lab19","lab20")
)

## Sort the data three times
## Create result by selecting first rows of every 5 rows 
mlb2 <- mlb[order(mlb[,1] %/% 5.1, mlb[,2], mlb[,1]),][mlb[,1] %% 5 == 1,]

## Exclude rows which mass_value > 2
(mlb3 <- mlb2[mlb2[,2] <= 2,])

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A R learner.
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