I came across the following seemingly bizarre behavior (this is a test case showing the basic issue).
from sympy import *
dz = symbols('dz')
f = 1/(dz - (1.0+I))
f1.series(dz,0,1)
this gives an error like "TypeError: gmpy.mpq() expects numeric or string argument"
On the other hand if I change 1.0 to just 1:
from sympy import *
dz = symbols('dz')
f = 1/(dz - (1+I))
f1.series(dz,0,1)
it gives the correct answer. Can someone explain me why?
You have to use the same name. In line 3 you use f as a name and in line 4 you use f1. Both versions give the same result when I tried them.
Related
The below line of code is returning as a 1 instead of a 2, for reasons I can't comprehend.
console.write(Format((87.20 \ 43.60)))
Surely this should return the result of 2 but I've checked in another environment and it returns a can anyone tell me why?
I have tried putting the code into a second environment but the result was the same I don't understand why it is returning 1 instead of 2, can anyone enlighten me?
Thanks for the help but found the answer.
Decimals are converted to Long before Integer division and due to this are subject to banker's rounding, multiplying both numbers by a 100 before the operation resolves the issue.
Source of information:
Learn Microsoft - VB.Net - \ Operator - Remarks
Thanks,
While I am glad you resolved your own question, I did want to provide an alternative.
When you use the integer division operator, you do not have control as to how the rounding should occur. Whereas if you do a floating-point division operator you can keep the precision and then use one of the built-in Math class methods (documentation) to specify how the number should round.
Take a look at this example:
Dim result = 87.20 / 43.60
Dim roundUp = Math.Ceiling(result)
Dim roundDown = Math.Floor(result)
Dim bankersRounding = Math.Round(result)
Fiddle: https://dotnetfiddle.net/LZEMXV
Because in your example you are using Console.Write (which treats the data as a String) you do not need to cast the value to an Integer data type. However, if you needed the value as an Integer, any one of those variables outside result can be safely converted to an Integer using the Parse method (documentation).
I hope you can help me. I'm looking for to classify some product based on the size: 40ML or other.
Here is my piece of code:
1. Dataframe creation
test = {'Name':['ProductA 40ML','ProductB 100ML','ProductC 40ML','ProductD 100ML']}
df1=pd.DataFrame(test)
2. Function built for classification
def size_class(row):
if row['Name'].str.contains('40ML'):
val = '40ML'
else:
val = 'other'
return val
df1['size_classification'] = df1.apply(size_class, axis=1)
Error message:
However the function returns the following error: AttributeError: 'str' object has no attribute 'str'
Question
Would you please be able to help me fix this one? I had a look at existing issues but couldn't find any answer addressing this.
I figure out some things you missed in your implementation:
In Python for most of the cases of membership tests, the operator in is more relevant than contains. Membership test operations documentation, see more details in this SOF question: Does Python have a string 'contains' substring method?
The default of the apply function is to look at the value of specific column, so you don't need to apply it on the whole data frame, but only on the relevant column.
The function applied with 'apply' looks separately on every cell's value. In your case, it's a string so you don't need to cast things.
So, the code that fixes your bugs is:
import pandas as pd
test = {'Name':['ProductA 40ML','ProductB 100ML','ProductC 40ML','ProductD 100ML']}
df1=pd.DataFrame(test)
def size_class(row):
if '40ML' in row:
val = '40ML'
else:
val = 'other'
return val
df1['size_classification'] = df1['Name'].apply(size_class)
print(df1.head())
I am trying to run several files of code for an assignment. I am trying to solve an optimization problem using the "quadprog" function from the "optim" package.
quadprog is supposed to solve the optimization problem in a certain format and takes inputs H,f, A,b, Aeq, Beq, lb, ub.
The issue I am having involves my f which is a column vector of constants. To clarify, f looks like c*[1,1,1,1,1,1] where c is a constant. Quadprog seems to run my code just fine for certain values of c, but gives me the error:
error: index (_,49): but object has size 2x2
error: called from
quadprog at line 351 column 32
for other values of c. So, for example, 1/3 works, but 1/2 doesn't. Does anyone have any experience with this?
Sorry for not providing a working example. My code runs over several files and I seem to only be having problems with a specific value set that is very big. Thanks!
You should try the qp native Octave function.
You mention f is: c*[1,1,1,1,1,1] but, if c is a scalar, that is not a column vector. It seems very odd that a scalar value might produce a dimensions error...
I am creating a function in Julia. It takes a dataframe (called window) and two strings (A and B) as inputs and subsets it using the variables given:
function calcs(window, A, B):
fAB=size(window[(window[:ref].==A).&(window[:alt].==B),:])[1]
end
But I get the error:
syntax: invalid assignment location ":fAB"
Stacktrace:
[1] include_string(::String, ::String) at ./loading.jl:522
I have tried running the code outside of a function (having pre-assigned the variables A="T" and B="C" like so:
fAB=size(window[(window[:ref].==A).&(window[:alt].==B),:])[1]
and this runs fine. I am new to Julia but cannot find an answer to this question. Can anyone help?
Seems you come from Python world. In Julia you do not need to add : in function definition. This will go through fine:
function calcs(window, A, B)
fAB=size(window[(window[:ref].==A).&(window[:alt].==B),:])[1]
end
When Julia encounters : in the first line of function definition it continues parsing the expression in the following line producing :fAB symbol.
EDIT: In Julia 0.7 this problem is detected by the parser. This is the result of copy-pasting your original code to REPL:
julia> function calcs(window, A, B):
fAB=size(window[(window[:ref].==A).&(window[:alt].==B),:])[1]
ERROR: syntax: space not allowed after ":" used for quoting
julia> end
ERROR: syntax: unexpected "end"
I am to be unable to get the following code to work. I know how to use python variables in queries, but somehow I can't get this right. The query works fine when I hard code the 'icaocode' variable in the query, but not if I try to use a variable. What is wrong with this code?
icaocode = input()
c.execute("SELECT EXISTS(SELECT 1 FROM airports WHERE ICAO = ?)", (icaocode))
if c.fetchone():
print("Found!")
else:
print("Not found...")
Received error:
sqlite3.ProgrammingError: Incorrect number of bindings supplied. The current statement uses 1, and there are 4 supplied.
In Python, wrapping an expression in parentheses does not make any difference, (icaocode) is exactly the same as icaocode.
The execute method expects some kind of list of parameters, so it sees the string as a sequence of four characters.
To tell Python that you want a tuple with a single element, you have to add a comma:
c.execute("... WHERE ICAO = ?", (icaocode,))