changing hash key

[Tim Wolak]

I've been looking for a way to change a hash key. In my code I'm trying
to change the key from a number to a string. Do I need to convert the
key to a string and put it new value in there or is my code wrong?

Thanks in advance,
Tim


def numbers
@skty = Hash.new(0)
@sktynl.each do |key, value|
if key <= "39"
key = "SKTY"
@skty[key] += value # !> instance variable @skty
not initialized
elsif key >="40"
key = "SKYNY"
@skty[key] += value
end

 

[Austin Ziegler]

I've been looking for a way to change a hash key. In my code I'm trying
to change the key from a number to a string. Do I need to convert the
key to a string and put it new value in there or is my code wrong?

def numbers
@skty = Hash.new(0)
@sktynl.each do |key, value|
if key <= "39"
key = "SKTY"
@skty[key] += value # !> instance variable @skty
not initialized
elsif key >="40"
key = "SKYNY"
@skty[key] += value
end

First, your comparison isn't against numbers, but against strings:

irb(main):001:0> "5" <= "40"
=> false

If your keys are truly numbers, use numeric comparisons.

Second, I suspect the problem isn't that @skty (which is a *really*
bad variable name, by the way) isn't initialized, but that @skty[key]
isn't initialized. Which is true because you're not initializing the
value, you're just providing a default value if the key isn't found.

If you need to initialize an unfound value, you need the block form of Hash.new:

@skty = Hash.new { |h, k| h[k] = 0 }

-austin

 

[Tim Wolak]

I posted that code after I fixed an error. It is getting initialized,
after I iterate over the hash its still printing out the numbers that
are account numbers for the keys. I need to get any numbers that are
less than 39 and put that in a new hash with the key as SKTY and all
values added together into a value for that key.

Hope that make more sense of that I'm trying to do.

Tim

@skty = Hash.new { |h, k| h[k] = 0 }

-austin

 

[Todd Benson]

I posted that code after I fixed an error. It is getting initialized,
after I iterate over the hash its still printing out the numbers that
are account numbers for the keys. I need to get any numbers that are
less than 39 and put that in a new hash with the key as SKTY and all
values added together into a value for that key.

Hope that make more sense of that I'm trying to do.

Tim

Let me see. You want to have a new hash called skty with keys skty
and sktny? That's confusing, mostly I think because of your choice of
variable names.

If you can be sure that all keys are comparable with each other (in
this case integers), here's very quick and dirty...

class Hash
def sum_values
values.inject {|s, i| s + i}
end
def partition_by part
h1 = self.reject {|k,v| k > part}
h2 = self.reject {|k,v| k <= part}
return h1, h2
end
end

h = Hash[1,5,2,6,3,7,4,8,5,9]
a, b = h.partition_by 3.5

h_new = {}
h_new['skty'] = a.sum_values
h_new['sktny'] = b.sum_values
p h_new

You could most of this with one line if you were so crazily inclined

Todd

 

[Todd Benson]

Let me see. You want to have a new hash called skty with keys skty
and sktny? That's confusing, mostly I think because of your choice of
variable names.

If you can be sure that all keys are comparable with each other (in
this case integers), here's very quick and dirty...

class Hash
def sum_values
values.inject {|s, i| s + i}
end

...or maybe better...

class Array
def sum
inject {|s, i| s + i}
end
end

..and then later...

h_new['skty'] = a.values.sum

All this would need to be refactored, of course, to be production-worthy.

Todd

 

[Tim Wolak]

Hmm ok then maybe changing the keys is not what I need to do then.

The reason I have skty and sktyny is that those are account names, sorry
should have stated that earlier. So I have a list of account numbers
and their balances, all accounts listed 500 through 539 should have a
key of skty and accounts with 540 through 550 should be sktyny. All the
account balances for skty should be combined into the value for skty
and all the balances should be combined for teh value of sktyny. Here
is the full code, I did not want to post a mile long request with it
all in there.

Tim



class SktyFut
attr_reader :acct

def initialize(filename)
@acct = File.new(filename, "r")
end

def future_data
@sktylist = Hash.new(0)
@acct.each do |list|
office = list[21..23]
if office == "RPT"
next
else
acctnum = list[24..28]
end
lv = list[217..230]
is_negative = list[215,1] == "-"
value = lv.to_f/100
value = -value if is_negative

# Add vales to hash

@sktylist[acctnum] += value
end
return @sktylist
end
end

class Calculate
attr_reader :sktyfuta, :sktyfutb
def initialize(sktyfuta, sktyfutb)
@sktyfuta = sktyfuta
@sktyfutb = sktyfutb
end

def data_comp
@sktyfuta.merge(@sktyfutb) { |key, old_value,
new_value| old_value - new_value }
end
#end
end

class FinalNum
attr_reader :sktynl
def initialize(sktynl)
@sktynl = sktynl
end

def numbers
@skty = Hash.new(0)
@sktynl.each do |key, value|
if key <= "539"
key.to_s
key = "SKTY"
@skty[key] += value
elsif key >="540"
key = "SKYNY"
@skty[key] += value
end
#@skty.each{ |key, value| puts "#{key} value
#{value}" }

end
end
end

Dir.chdir("/tmp")
post = SktyFut.new("SKTYFutBal20080513.txt")
a = post.future_data
#a.each{|key, value| puts "#{key} value is #{value}"}
pre = SktyFut.new("SKTYFutBal20080512.txt")
b = pre.future_data
data = Calculate.new(a,b)
iteration = data.data_comp
iteration.sort
#iteration.each{|key, value| puts "#{key} comp equals #{value}" }
sktyfinal = FinalNum.new(iteration)
submission = sktyfinal.numbers
submission.each{ |key, value| puts "#{key} line is #{value}" }

 

[Todd Benson]

Hmm ok then maybe changing the keys is not what I need to do then.

The reason I have skty and sktyny is that those are account names, sorry
should have stated that earlier. So I have a list of account numbers
and their balances, all accounts listed 500 through 539 should have a
key of skty and accounts with 540 through 550 should be sktyny. All the
account balances for skty should be combined into the value for skty
and all the balances should be combined for teh value of sktyny. Here
is the full code, I did not want to post a mile long request with it
all in there.

Tim



class SktyFut
attr_reader :acct

def initialize(filename)
@acct = File.new(filename, "r")

I'm not sure ruby automagically closes the file when the instance of
SktyFut is garbage collected. You open a file and assign it to a
class instance variable. Looks a little scary to me.

end

def future_data
@sktylist = Hash.new(0)
@acct.each do |list|
office = list[21..23]
if office == "RPT"
next
else
acctnum = list[24..28]
end
lv = list[217..230]
is_negative = list[215,1] == "-"
value = lv.to_f/100
value = -value if is_negative

value = list[215..230].delete(' ').to_f/100
# if the character separating - from lv is a space

# Add vales to hash

@sktylist[acctnum] += value
end
return @sktylist
end
end

class Calculate
attr_reader :sktyfuta, :sktyfutb
def initialize(sktyfuta, sktyfutb)
@sktyfuta = sktyfuta
@sktyfutb = sktyfutb
end

def data_comp
@sktyfuta.merge(@sktyfutb) { |key, old_value,
new_value| old_value - new_value }
end
#end
end

class FinalNum
attr_reader :sktynl
def initialize(sktynl)
@sktynl = sktynl
end

def numbers
@skty = Hash.new(0)
@sktynl.each do |key, value|
if key <= "539"

key.to_s
key = "SKTY"
@skty[key] += value

replace above 3 lines with... @skty["SKTY"] += value

elsif key >="540"
key = "SKYNY"
@skty[key] += value

replace above 3 lines with... @skty["SKYNY"] += value
or SKTYNY or whatever it is you are using

end
#@skty.each{ |key, value| puts "#{key} value
#{value}" }

Here should be... return @skty

end
end
end

Dir.chdir("/tmp")
post = SktyFut.new("SKTYFutBal20080513.txt")
a = post.future_data
#a.each{|key, value| puts "#{key} value is #{value}"}
pre = SktyFut.new("SKTYFutBal20080512.txt")
b = pre.future_data
data = Calculate.new(a,b)
iteration = data.data_comp
iteration.sort
#iteration.each{|key, value| puts "#{key} comp equals #{value}" }
sktyfinal = FinalNum.new(iteration)
submission = sktyfinal.numbers
submission.each{ |key, value| puts "#{key} line is #{value}" }

For the #numbers method, you might someday want to check out #select.
For example.

skny_sum = @sktynl.select {|k, v| k < 540}.inject(0) {|sum, arr| sum + arr[1]}

hth,
Todd

 

[Adam Shelly]

Hmm ok then maybe changing the keys is not what I need to do then.

The reason I have skty and sktyny is that those are account names, sorry
should have stated that earlier.

You can still use readable variable names in the code. (What if you
wanted to run the same algorithm on two different accounts?). A
better idea might be to name your hash @account_balances, and store
the account names as strings.

So I have a list of account numbers

and their balances, all accounts listed 500 through 539 should have a
key of skty and accounts with 540 through 550 should be sktyny. All the
account balances for skty should be combined into the value for skty
and all the balances should be combined for teh value of sktyny.

So what about something like
account_map = {
"sticky" => (500..539),
"stinky" => (540..550)
}
# fill @account_balances...

account_summary= Hash.new
account_map.each{|name,range|
account_summary[name]= @account_balances.select{|act_num, balance|
range.include? (act_num)
}
}
account_summary.each{|name, subtotals|
total = subtotals.map{|act_num,balance|balance}.sum
puts "#{name} has a balance of #{total}"
}



-Adam

 

[Todd Benson]

account_map = {
"sticky" => (500..539),
"stinky" => (540..550)
}
# fill @account_balances...

account_summary= Hash.new
account_map.each{|name,range|
account_summary[name]= @account_balances.select{|act_num, balance|
range.include? (act_num)
}
}
account_summary.each{|name, subtotals|
total = subtotals.map{|act_num,balance|balance}.sum

Just FYI to ruby nubies: The #sum method for addition in enumerables
is available in libraries (included with Rails, for example), but not
in ruby 1.8.6 itself. I don't know the status of ruby 1.9 on that
one.

Todd

 

[7stud --]

Hmm ok then maybe changing the keys is not what I need to do then.

The reason I have skty and sktyny is that those are account names, sorry
should have stated that earlier. So I have a list of account numbers
and their balances, all accounts listed 500 through 539 should have a
key of skty and accounts with 540 through 550 should be sktyny. All the
account balances for skty should be combined into the value for skty
and all the balances should be combined for teh value of sktyny. Here
is the full code, I did not want to post a mile long request with it
all in there.

#Create a hash so a non-existent key returns
#the default value 0:
results = Hash.new {|hash, key| hash[key] = 0}

key1 = "skty"
range1 = 500..539

key2 = "sktyny"
range2 = 540..550

DATA.each_line do |line|
acct_str, balance_str = line.split

acct = acct_str.to_i
balance = balance_str.to_f

if range1 === acct
results[key1] += balance
elsif range2 === acct
results[key2] += balance
else
results[acct] = balance
end

end

p results
__END__
440 550.25
539 22.25
500 10.50
540 100.00
550 225.00
100 300.00

--output:--
{"sktyny"=>325.0, 440=>550.25, 100=>300.0, "skty"=>32.75}