So I have this homework assignment that requires me to assign output to labels after I compare two arrays. My problem is that after I compare the two arrays, the output I assign is wrong. I'm supposed to out 'Y' if at a specific index of the two arrays are equal and 'N' if they're not equal but every time I run the code, it outputs 'Y' to all the labels no matter what. How can I fix what is being outputted after the comparison?
private void evaluateStudentAnswers()
{
/* Use a "for" loop to cycle through the answerKey[] and studentAnswers[] arrays, and compare the answers
* in the two arrays at each index. If they match, then increment the global variable "correctAnswers"
* and assign the value 'Y' to the corresponding index in the correctOrIncorrect[] array. if they
* don't match, then increment the global variable "incorrectAnswers" and assign the value 'N' to the
* corresponding indes in the correctOrIncorrec[] array. These two variables will be used to calculate
* the grade percentage.
*/
for (int i = 0; i < studentAnswers.Length; i++)
{
for(int j = 0; j < answerKey.Length; j++)
{
// I think the indexes below are being checked if they're the same and I need to make sure not just the
//indexes are the same but the values as well
if (studentAnswers[i] == answerKey[j])
{
correctAnswers++;
for(int k = 0; k < correctOrIncorrect.Length; k++)
{
correctOrIncorrect[k] = 'Y';
}
}
else
{
incorrectAnswers++;
for (int k = 0; k < correctOrIncorrect.Length; k++)
{
correctOrIncorrect[k] = 'N';
}
}
}
}
}
I think your code can be simplified quite a lot. assuming there's a 1-1 mapping between studentAnswers and answerKey.
for (int i = 0; i < studentAnswers.Length; i++)
{
var studentAnswer = studentAnswers[i];
var answer = answerKey[i];
if (studentAnswer == answer)
{
++correctAnswers;
correctOrIncorrect[i] = 'Y';
}
else
{
++incorrectAnswers;
correctOrIncorrect[i] = 'N'
}
}
All of the arrays are the same size. So when we loop over each answer the student provided, we know we can find the corresponding correct answer in answerKey. Also, the tracking of correct answers also follows the same pattern, for each studentAnswer, we want to record the correctness in correctOrIncorrect, which corresponds to the particular answer the student provided. As such, we only need to perform a single loop, since the i refers to the appropriate index in all the arrays as we're processing.
If studentAnswers.Length == answerKey.Length == correctOrIncorrect.Length
Then
for (int i = 0; i < studentAnswers.Length; i++)
{
if(studentAnswers[i] == answerKey[j])
{
correctAnswers++;
correctOrIncorrect[k] = 'Y';
}
else
{
incorrectAnswers++;
correctOrIncorrect[k] = 'N';
}
}
Since it is an assignment I wont give an answer :) but since you are stuck I encourage you use the guidance below.
These two are unnecessary in your code
inner for-loop on correctOrIncorrect[]
variable "k", you can use "i" instead for correctOrIncorrect value assignment
Since the arrays have to have the same size/order, you only need to loop through them once. Also I find ternary assignments more clear than if blocks:
Func<bool, int> toInt = (b) => b ? 1 : 0;
for (int i = 0; i < studentAnswers.Length; i++)
{
var studentAnswer = studentAnswers[i];
var answer = answerKey[i];
var isCorrect = studentAnswer == answer;
correctOrIncorrect[i] = isCorrect ? 'Y' : 'N';
correctAnswers = isCorrect ? 1 : 0; // toInt(isCorrect)
incorrectAnswers = !isCorrect ? 1 : 0; // toInt(!isCorrect)
}
}
Or in LINQ (just because it's worth learning, but probably not appropriate for homework):
correctOrIncorrect = answerKey.Zip(studentAnswer, (a,b) => a == b ? "Y" : "N").ToArray();
incorrectAnswers = correctOrIncorrect.Count(x => x == "Y");
...
Related
I have a function that estimates correlation between two input arrays.
The input is feeded by a dataDict which is of type Dictionary<string, double[]> which has 153 keys with values as double array of size 1500.
For each individual key, I need to estimate its correlation with all other keys and store the result to a double[,] that has a size of double[dataDict.Count(), dataDict.Count()]
The following function prepares two double[] arrays whose correlation needs to be estimated.
public double[,] CalculateCorrelation(Dictionary<string, double?[]> dataDict, string corrMethod = "kendall")
{
CorrelationLogicModule correlationLogicModule = new CorrelationLogicModule();
double[,] correlationMatrix = new double[dataDict.Count(), dataDict.Count()];
for (int i = 0; i < dataDict.Count; i++)
{
for (int j = 0; j < dataDict.Count; j++)
{
var arrayA = dataDict[dataDict.ElementAt(i).Key].Cast<double>().ToArray();
var arrayB = dataDict[dataDict.ElementAt(j).Key].Cast<double>().ToArray();
correlationMatrix[i, j] = correlationLogicModule.Kendall_Formula(arrayA, arrayB);
}
}
return correlationMatrix;
}
The following function (I found it on internet from here) finds correlation between two input arrays using 'Kendall's' method.
public double Kendall_Formula(double[] Ticker1, double[] Ticker2)
{
double NbrConcord, NbrDiscord, S;
NbrConcord = 0;
NbrDiscord = 0;
S = 0;
for (int i = 0; i < Ticker1.Length - 1; i++)
{
for (int j = i + 1; j < Ticker1.Length; j++)
{
//Compute the number of concordant pairs
if (((Ticker1[i] < Ticker1[j]) & (Ticker2[i] < Ticker2[j])) | ((Ticker1[i] > Ticker1[j]) & (Ticker2[i] > Ticker2[j])))
{
NbrConcord++;
}
//Compute the number of discordant pairs
else if (((Ticker1[i] > Ticker1[j]) & (Ticker2[i] < Ticker2[j])) | ((Ticker1[i] < Ticker1[j]) & (Ticker2[i] > Ticker2[j])))
{
NbrDiscord++;
}
}
}
S = NbrConcord - NbrDiscord;
//Proportion with the total pairs
return 2 * S / (Ticker1.Length * (Ticker1.Length - 1));
}
Moving this way forward, takes a very long time to calculate the correlations for all the keys.
is there a possible way to optimize the performance?.
I am new to C# but I have been using Python for a long time and in Python using 'Numpys' and 'Pandas' I am sure the above operation would take seconds to compute. For e.g. lets say I had the above data in form of a pandas dataframe, then data[[list of columns]].corr('method') would lead the result in seconds. This is because pandas uses numpy under the hood which takes benefit from vectorization. I would like to learn how can I take benefit from vectorization to improve the performance of the above code in C# and if there are other factors I need to consider. Thank you!
You are using dataDict[dataDict.ElementAt(i).Key] to access the dictionary values in an undefined order. I don't know if that's what you intended, but the following code should give the the same results.
If you call dataDict.Values.ToArray(); you will get the dictionary values in the same order as you would when using foreach to iterate over it. That means that it will be the same as the order when using dataDict[dataDict.ElementAt(i).Key].
Therefore this code should be equivalent, and it should be faster:
public double[,] CalculateCorrelation(Dictionary<string, double?[]> dataDict, string corrMethod = "kendall")
{
CorrelationLogicModule correlationLogicModule = new CorrelationLogicModule();
var values = dataDict.Values.Select(array => array.Cast<double>().ToArray()).ToArray();
double[,] correlationMatrix = new double[dataDict.Count, dataDict.Count];
for (int i = 0; i < dataDict.Count; i++)
{
for (int j = 0; j < dataDict.Count; j++)
{
var arrayA = values[i];
var arrayB = values[j];
correlationMatrix[i, j] = correlationLogicModule.Kendall_Formula(arrayA, arrayB);
}
}
return correlationMatrix;
}
Note that the .ElementAt() call in your original code is a Linq extension, not a member of Dictionary<TKey,TValue>. It iterates from the start of the dictionary EVERY TIME you call it - and it also returns items in an unspecified order. From the documentation: For purposes of enumeration, each item in the dictionary is treated as a KeyValuePair<TKey,TValue> structure representing a value and its key. The order in which the items are returned is undefined.
Also:
You should change the bitwise & to logical && in your conditions. The use of & will prevent the compiler applying a boolean short-circuit optimisation, meaning that all the < / > comparisons will be performed, even if the first condition is false.
Hey I'm in a situation where I have a for loop that does some stuff and I want to make a line of code either call a function passing in an array indexed by the for loops index, or run a single (not array) variable for every call of that function, I know I could do that by putting an if statement inside the for loop but i'd be repeating the same if statement over and over getting the same result. So is there a way good way I can run the if statement before the for loop and the result of that if statement run the same for loop but that one call passes in the array or the variable?
Code Example
for (int i = 0; i < CurrentVerticalList.Count; i++)
{
GuiGeneral CGroup = CurrentVerticalList[i];
CGroup.ResizeUsingStandard(ForcedResize[i]); //I want the condition before the for
//loop to have ForcedResize[i] here if
//true and another variable here of the
//same type but not an array if false.
for (int j = 0; j < 2; j++)
{
GlobalListIndex[j]++;
}
CGroup.MoveElementTo(CCoord, false);
CCoord.y += CGroup.ElementRect.WidthHeight.y;
}
Here you go, moving your condition check out of your for loop:
Func<int, double> GetResizeFromForcedResize = (index => ForcedResize[index]);
Func<int, double> GetResizeFromVariable = (index => fixVariable);
var GetResizeValue = condition? GetResizeFromForcedResize : GetResizeFromVariable;
for (int i = 0; i < CurrentVerticalList.Count; i++)
{
GuiGeneral CGroup = CurrentVerticalList[i];
CGroup.ResizeUsingStandard(GetResizeValue(i));
for (int j = 0; j < 2; j++)
{
GlobalListIndex[j]++;
}
CGroup.MoveElementTo(CCoord, false);
CCoord.y += CGroup.ElementRect.WidthHeight.y;
}
Edit: Wanted to let you know that the other answers here are still doing a check at every iteration, but not this one.
Eh, hard to understand the question to me but i recon what you want is something along these lines, could've helped with more types supplied, but you could make the intend achievable using a local function:
ForcedResizeArrayType other = new object(); //TODO: Define return type
bool condition = ResolveCondition(); //TODO: Define condition to be true or false
ForcedResizeArrayType GetOneOr(int i, bool condition,
ForcedResizeArrayType[] forcedResizeArray)
{
return condition ? forcedResizeArray[i] : other;
}
for (int i = 0; i < CurrentVerticalList.Count; i++)
{
CGroup.ResizeUsingStandard(GetOneOr(i, condition, ForcedResize));
}
It varies from week to week if i love or hate those local functions, but they have uses
In my code I have string array of 1000 indexes and it contain unique string data. Now, I want to make duplicate of some of them string element without overwriting next element. To summarize I would like to shift the array and inserting a duplicate value.
Here my code is,
for (int r = 0; r < sResultarray1.Length; r++)
{
if (sResultarray1[r] != null &&
sResultarray1[r].Contains("WP") &&
sResultarray1[r].Contains("CB") == true)
{
index = Array.IndexOf(sResultarray1, sResultarray1[r]);
for (int e = 1000; e >= index + c; e--)
{
sResultarray1[e] = sResultarray1[e - c];
}
break;
}
}
My current output is
++ST110+WP001.CB001
++ST120+WP001.CB001
++ST120+WP002.CB001
++ST130+WP001.CB001
++ST110+WP001.CB001
++ST120+WP001.CB001
++ST120+WP002.CB001
++ST130+WP001.CB001
My desired output is
++ST110+WP001.CB001
++ST110+WP001.CB001
++ST120+WP001.CB001
++ST120+WP001.CB001
++ST120+WP002.CB001
++ST120+WP002.CB001
++ST130+WP001.CB001
++ST130+WP001.CB001
Does anyone help me out to solve this problem?
I suggest using different collection type - List<string> instead of String[] (at least temporarily): Add, Insert ("shift and add") are not operations array has been designed for. Something like this:
using System.Linq;
...
// Temporal collection - list
List<string> list = sResultarray1.ToList();
// Downward - we don't want to check the inserted item
for (int r = list.Count - 1; r >= 0; --r) {
if (list[r] != null && list[r].Contains("WP") && list[r].Contains("CB")) {
// if you want to insert - "shift and add duplicate value" - just insert
list.Insert(r + 1, list[r]);
}
}
// back to the array
sResultarray1 = list.ToArray();
I'm trying to sort a list of strings in alphabetical order in C#. My code looks like this:
public static List<Result> sort(List<Result> listToSort)
{
int listSize = listToSort.Count;
for (int i = 0; i < listSize; i++)
{
for (int j = 0; j < listSize; j++)
{
if (listToSort[i].SN[0] < listToSort[j].SN[0])
{
Result tempValue = listToSort[j];
listToSort[j] = listToSort[i];
listToSort[i] = tempValue;
}
}
}
return listToSort;
}
But it's only sorting it based on the first letter of a string. In other words, if I have a list like this:
donald, abby, dave, bob, sam, pete
It will sort it like so:
abby, bob, donald, dave, pete, sam
One would expect 'dave' to come before 'donald'..
Any ideas?
Currently you are only sorting by the first letter that is why you are seeing this result. You can use Enumerable.OrderBy - LINQ
List<Result> sortedList = listToSort.OrderBy(r=> r.SN).ToList();
Or for your current code you can modify your check to:
if (string.Compare(listToSort[i].SN,listToSort[j].SN) < 0)
How about using LINQ for this:
return listToSort.OrderBy(report => report.SN)
I'm assuming your Report class has a string property you want the list to be sorted by?
EDIT
Didn't notice that you'd already specified the SN property, have amended my answer.
public static List<Result> sort(List<Result> listToSort)
{
return listToSort.OrderBy(x=>x.SN[0]).ToList();
}
You're only ever evaluating the first letter. Try using the traditional sorting method:
public static void Sort(List<Result> listToSort)
{
listToSort.Sort(new ResultComparator());
}
public class ResultComparator : IComparer<Result>
{
public int Compare(Result x, Result y)
{
if (x == null && y == null) return 0;
if (x == null) return 1;
if (y == null) return 0;
// compare based in SN
return string.Compare(x.SN, y.SN);
}
}
Take a look at this part:
for (int i = 0; i < listSize; i++)
{
for (int j = 0; j < listSize; j++)
{
if (listToSort[i].SN[0] < listToSort[j].SN[0])
{
You are
only comparing on SN[0]. If SN is a string then that explains your main result.
always using the same compare, whether i < j or i > j
Best thing to do is to use a built-in sort. Linq's OrderBy(lambda) is the easiest but it creates a new list. For an in-place sort, use List<T>.Sort(Comparer).
If you do have to do it yourself, look up a good sorting algorithm (wikipedia).
It was happened because of comparing character of the first string (listToSort[i].SN[0] => which produces the first character of your input). If you want to compare the string values, you should use string.Compare() method.
--SJ
Basically comparing a string that is entered, and trying to get that position from the array.
If I initialize position to 0 then it returns the position zero of the array, if I initialize to 1 then it gives me the item in slot 1, so it's skipping the compare statement.
I also tried using (custStatus == cardStatus[i])
public static int discount(string []cardStatus, int []pDiscount, string custStatus)
{
int position= 0;
int discount;
for(int i = 0; i < 2; i++)
{
if (string.Equals(custStatus, cardStatus[i]))
position = i;
}
discount = pDiscount[position];
return discount;
}
With your code, there's no way to tell if position = 0 means custStatus was found in your cardStatus array or if no match was made at all and the default value is being used. I'd recommend either using a boolean matchFound variable or setting position = -1 and adding an extra if statement at the end either way. Either:
boolean matchFound = false;
...
if(matchFound)
{
discount = pDiscount[position];
}
or else
int position = -1;
...
if(position >= 0)
{
discount = pDiscount[position];
}
Give this a try:
public static int discount(string[] cardStatus, int[] pDiscount, string custStatus) {
var position = Array.IndexOf(cardStatus, custStatus);
return (position == -1) ? -1 : pDiscount[position];
}
public static int discount(string []cardStatus, int []pDiscount, string custStatus)
{
for(int i = 0; i < Math.Min(cardStatus.Length, pDiscount.Length); i++)
{
if (string.Equals(custStatus, cardStatus[i]))
{
return pDiscount[i];
}
}
return -1;
}
Don't be afraid to return directly from FOR-loop, it is old-school that teaches to have only one return point from method. You can have as many returns as it helps you to keep your code clean and easy to read.
And perhaps it would be better to use the following expression in for-loop as it will guard you from possible different lengths of arrays:
for (int i = 0; i < Math.Min(cardStatus.Length, pDiscount.Length; i++)
This looks ok, even though this is somewhat more straightforward:
for(int i = 0; i < cardStatus.Length; i++)
{
if (custStatus == cardStatus[i])
{
position = i;
break;
}
}
Given your question it appears to be the case that all cardStatus[i] match custStatus - did you check the input?
Also given your code what happens if there is no match? Currently you would return pDiscount[0] - that doesn't seem to be correct.