Lua - Analysing values in a text file - lua

Question

I’m writing power (watts) values to a text file in order to extract information I can use.
4.7
4.7
4.8
5.2
5.1
4.6
4.6
4.6
Currently I have the following code to give me the average, but I’d like to add to it so it tells me more such as, what was the highest value, the lowest value, the most frequent value, and if at all possible if there are any ‘0’ values recorded (* - if possible with that last one it would be good to ignore them..)
local ctr = 0
local sum = 0
for _ in io.lines"/www/EnergyPlug-b.txt" do
ctr = ctr + 1
end
print(ctr)
for line in io.lines"/www/EnergyPlug-b.txt" do
sum = sum + line
end
print(sum)
average = sum / ctr
print(average)
I did explore creating a Lua table via table.insert() off of the first io.lines section, like the following, but I’m not sure how good it is?
local rows = {}
-- go over the file line by line
for line in io.lines("/www/EnergyPlug-b.txt") do
-- if line matches ?.? then insert into table
local value = line:match("%d%p%d") -- 1.5
--print(value)
table.insert(rows, value)
end
local arraymax = math.max(unpack(rows))
local arraymin = math.min(unpack(rows))
print (arraymax) -- ?.?
print (arraymin) -- ?.?
If the above is suitable, how best should I go about identifying the items/values i mentioned at the very start ?

Answer 1

In the first snippet there is no reason to have a separate loop for ctr and sum. You can do it in one loop.
Your second snipped is ok. unpack is limited so this won't work for many thousand values.
You have to traverse the table anyway to get the other values so you can determin min and max in that loop too without that size limit.
local value = line:match("%d%p%d") if there are only those numbers in that file you can skip the pattern matching here.
The calculations are pretty straigt forward. I'm not sure what you're struggling with here.
local min = math.huge -- use a value that is definitely bigger than any value
local max = -math.huge -- use a value that is definitely smaller than any value
local counts = {} -- an emtpy table we'll use to count how often each value occurs
local numIngored = 0 -- how many 0 values have we ignored?
for line in io.lines(yourFileName) do
-- convert string to a number
local value = tonumber(line)
-- if we take the value into account
if value ~= 0.0 then
-- update min and max values
min = value < min and value or min
max = value > max and value or max
-- update counts
counts[value] = counts[value] and counts[value] + 1 or 1
else
-- count ignored values
numIgnored = numIgnored + 1
end
end
I'll leave it up to you to get the most frequent values from counts

Answer 2

Thanks to #piglet and using other SO posts, here is what I ended up with..
local min = math.huge -- use a value that is definitely bigger than any value
local max = -math.huge -- use a value that is definitely smaller than any value
local ctr = 0
local valtotal = 0
local counts = {} -- an emtpy table we'll use to count how often each value occurs
local numIngored = 0 -- how many 0 values have we ignored?
for line in io.lines("/www/EnergyPlug-b.txt") do
-- convert string to a number
local value = tonumber(line)
-- if we take the value into account
if value ~= 0.0 then
ctr = ctr + 1
valtotal = valtotal + value
-- update min and max values
min = value < min and value or min
max = value > max and value or max
-- update counts
counts[value] = counts[value] and counts[value] + 1 or 1
else
-- count ignored values
numIgnored = numIgnored + 1
end
end
print("----Table print out -----")
for k, v in pairs(counts) do
print(k,v)
end
print("---------------------------")
print("Lowest value recorded = " ..min)
print("Highest value recorded = " ..max)
print("Average value recorded = " ..round2(valtotal / ctr, 1))
print("Number of values recorded = " ..ctr)
print("---------------------------")
local max_val, key1 = -math.huge
for k, v in pairs(counts) do
if v > max_val then
max_val, key1 = v, k
end
end
local min_val, key2 = math.huge
for k1, v1 in pairs(counts) do
if v1 < min_val or v1 == min_val then
min_val, key2 = v1, k1
end
end
local min_qty, max_qty = 0, 0
local min_str, max_str = "", ""
for k2, v2 in pairs(counts) do
if v2 == min_val then
min_qty = min_qty + 1
min_str = min_str .. " " .. k2
elseif v2 == max_val then
max_qty = max_qty + 1
max_str = max_str .. " " .. k2
end
end
if min_qty == 1 then
print("Least recorded value was = " ..key2.. " recorded "..min_val.." times")
else
print("Least recorded values were = " ..min_str.. " each recorded "..min_val.." time")
end
if max_qty == 1 then
print("Most recorded value was = " ..key1.. " recorded "..max_val.." times")
else
print("Least recorded values were = " ..max_str.. " each recorded "..max_val.." time")
end
print("---------------------------")