Store unknown length results of a nested loop-CodePudding

I got a nested loop:

SA_range <- seq(0.01, 89.99, by = 0.01)
SR_value <- c(0.182, 0.307, 0.408, 0.603, 0.720, 0.823, 0.998)

library(tidyverse)
library(pracma)

for (i in SR_value) {
  for (j in SA_range) {
    if (near((cot(j*(pi/180))*log(tan(j*(pi/180))   sec(j*(pi/180)))), # my formula
             i, 
             tol = 0.0002)) {
      print(c(i, j))
    } 
  }
}

What I'm trying to do here is substituting every number from SA_range into the formula to see if the formula output matches values in SR_value, and if the output does match SR_value at the given accuracy (0.0002), then print SR_value and corresponding value(s) in SA_range.

The loop works fine but the problem to me is storing the results (currently I can only print them). The challnege is that my actual SR_value has a lot more values than this example and sometime mutiple values in SA_range can be found by the loop. For example, when SR = 0.182, there is only one SA value matches the formula output, but when SR = 0.998, there are 63 SA values match the output! (code not shown here to save space)

So basically, assume the length of results of this loop is unknown, how can I store all the results?

(This is a case of solving an equation by iteration, so any other efficient methods are also welcome!)

CodePudding user response：

You can try -

SA_range <- seq(0.01, 89.99, by = 0.01)
SR_value <- c(0.182, 0.307, 0.408, 0.603, 0.720, 0.823, 0.998)

library(tidyverse)
library(pracma)
results <- list()
k <- 0
for (i in SR_value) {
  for (j in SA_range) {
    value <- (cot(j*(pi/180))*log(tan(j*(pi/180))   sec(j*(pi/180))))
    if (near(value, i, tol = 0.0002)) {
      k <- k   1
      results[[k]] <- c(i, j)
    } 
  }
}
results

#[[1]]
#[1]  0.182 87.190

#[[2]]
#[1]  0.307 84.080

#[[3]]
#[1]  0.307 84.090

#[[4]]
#[1]  0.408 80.800

#[[5]]
#[1]  0.408 80.810
#...

CodePudding user response：

Solution for your usecase:

results <- list()
for (i in SR_value) {
  SAresults <- numeric()
  for (j in SA_range) {
    if (near((cot(j*(pi/180))*log(tan(j*(pi/180))   sec(j*(pi/180)))), # my formula
         i, 
         tol = 0.0002)) {
      SAresults <- c(SAresults, j)
    } 
  results[[as.character(i)]] <- SAresults  
  }
}

A minimal reproducible example of the suggested solution:

SA_range <- seq(0.01, 89.99, by = 0.01)
SR_value <- c(0.182, 0.307, 0.408, 0.603, 0.720, 0.823, 0.998)


results <- list()
for (i in SR_value) {
  SAresults <- numeric()
  for (j in SA_range) {
    if (j < 0.03) {
      SAresults <- c(SAresults, j)
    } 
  results[[as.character(i)]] <- SAresults  
  }
}

results

Returns:

$`0.182`
[1] 0.01 0.02

$`0.307`
[1] 0.01 0.02

$`0.408`
[1] 0.01 0.02

$`0.603`
[1] 0.01 0.02

$`0.72`
[1] 0.01 0.02

$`0.823`
[1] 0.01 0.02

$`0.998`
[1] 0.01 0.02