differential equations – NDSolve methods

In solving a large system of ODEs I found that Method->ExplicitRungeKutta (also Automatic as a matter of fact) is fast, but often unstable. I tried the option Method->ImplicitRungeKutta, but for the given number of ODEs (3924) the memory used by the kernel grows above 50GB. Eventually I have to stop the calculation. What options of NDSolve can be tried to improve the stability and remain with reasonable memory consumption?

st.statistics – Tools and methods for explore Quantitative to Categorical association

I’m current takint the Statiscal Reasoning course. It presents how to explore the relationship in three of the four cases of the role-type classification.

The only one not included is for the case of a quantitative explanatory variable and a categorical response variable.

Googling around I was unable to find resources on this kind of analysis. Any direction or suggestions?

Quantifying the impact of offering alternative signup/login methods?

Nowadays it’s common for websites to offer signup/signin methods that don’t require making an account (email/password) for that specific site, for example ‘Login with x’:

  • Facebook
  • Google
  • Twitter
  • LinkedIn
  • etc

By how much does offering each common alternative signup method increase the signup rate for an average website, as opposed to just offering traditional email/password signup?


  • Obviously these statistics could differ (a lot) from site to site, depending on the demographic and other factors. But I currently have very little idea of how much impact each signup method has, so any information is a massive improvement on that

  • Very interested to know if any studies have been conducted, or if any companies (big or small) have released statistics.


Suppose a website only offered the traditional username/password signup method and it signed up 1% of the visitors to the site, but then it got a ‘Login with Google’ feature, and its signup rate went to 1.1%, then we could very roughly guess the ‘Login with Google’ feature increased the signup rate by 10%. (figures completely made up)

unity – Error CS0116: A namespace cannot directly contain members such as fields or methods

I have a problem in line 63,10.

The error I have to change is in line 63 is void CrosshairChange(bool on)

Here is the code:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class DoorRaycast : MonoBehaviour
(SerializeField) private int rayLength = 5;
(SerializeField) private LayerMask layerMaskInteract;
(SerializeField) private string excludeLayerName = null;

private MyDoorController raycastedObj;

(SerializeField) private KeyCode openDoorKey = KeyCode.Mouse0;

(SerializeField) private Image crosshair = null;
private bool isCrosshairActive;
private bool doOnce;

private const string interactableTag = "InteractiveObject";

private void Update()
    RaycastHit hit;
    Vector3 fwd = transform.TransformDirection(Vector3.forward);

    int mask = 1 << LayerMask.NameToLayer(excludeLayerName) | layerMaskInteract.value;

    if (Physics.Raycast(transform.position, fwd, out hit, rayLength, mask))
        if (hit.collider.CompareTag(interactableTag))
            if (!doOnce)
                raycastedObj = hit.collider.gameObject.GetComponent<MyDoorController>();
    }       isCrosshairActive = true;
            doOnce = true;

    if (Input.GetKeyDown(openDoorKey))

    } if (isCrosshairActive)
        doOnce = false;


void CrosshairChange(bool on)
    if (on && !doOnce)
        crosshair.color = Color.red;
        crosshair.color = Color.white;
        isCrosshairActive = false;


How can formal methods be used to ensure the separation logic?

How can formal methods be used to ensure the separation logic (one important aspect is the separation of information between different levels of classified information)? Do you know of any projects where they try this?

integration – Are there clever methods to solve this indefinite integral?

I’m curious about knowing if there is any other method to solve this indefinite integral
int frac{sqrt{x}}{1+x^{2}},dx

besides set $ sqrt{x} = t $ and obtain
int frac{2t^{2}}{1+t^{4}},dt

where i know i can reduce the problem to the resolution of
int frac{t^{2}}{1+t^{4}},dt

and factorize $1+t^{4}$ as $(t^{2}+sqrt{2}t^{2}+1)cdot(t^{2}-sqrt{2}t^{2}+1)$
reducing the integral to the form

int frac{t^{2}}{(t^{2}+sqrt{2}t^{2}+1)cdot(t^{2}-sqrt{2}t^{2}+1)},dt

that is not impossible with partial fraction but still tedious

amazon web services – How to retrieve a Lambda function’s associated API Gateway methods with boto3

I’m trying to write a Python script that lets you rename a Lambda function by copying all of the code and configuration to a new function. As part of that process, I want to take all of the API Gateway methods that point to the old function and redirect them to point to the new function.

Is there a way to accomplish this with boto3?

c# – Simplifying these methods for iterating through object and modifying string fields

I have this method (consisting of three methods) that I need to use for looking through objects that are going to be serializes and logged as json objects.

a bit of intro (not necessary to read)

The initial problem was that I noticed that sometimes I would receive data in objects from external api’s that would contain personal sensitive data i.e social security numbers. I would still like to log these objets though, I just want to sanitize the social sec numbers away, and I also would like to have some method that could this for object with any kind of internal structure, such that I could reuse it, and would’nt need to rewrite a new sanitization method for each log.

The problem

So now I wanted these methods that could look into objects of any type, and sanitize all the string fields, such that the strings would look the same, but for any string field with a social security number of the type 123456-7891, should be replaced with XXXXXX-XXXX.

   public static  void DoitNow(object obj)
        Queue<PropertyInfo> properties = new Queue<PropertyInfo>(obj.GetType().GetProperties());
        while (properties.Count != 0)
            PropertyInfo property = properties.Dequeue();

            if (property.GetValue(obj) is string)

                string stringField = property.GetValue(obj).ToString();

                String sanitizedField = sanitizeSensitiveString(stringField);
                property.SetValue(obj, sanitizedField);

            else if (property.GetValue(obj) is IList)
                IList y = (IList)property.GetValue(obj);

                if (y.Count != 0)
                    if (y(0) is string)
                        for (int i = 0; i < y.Count; i++)
                            y(i) = sanitizeSensitiveString((string)y(i));
                    else if (IsNested(y(0)))
                        for (int i = 0; i < y.Count; i++)
            else if (IsNested(property.GetValue(obj)))

                var l = property.GetValue(obj);


    public static string sanitizeSensitiveString(string sensitiveString)
        return Regex.Replace(sensitiveString, @"d{6}-?d{4}(0-9)*", " XXXXXX-XXXX ");
    public static bool IsNested(object value)
        Type t = value.GetType();
        if (t.IsPrimitive || value is string)
            return false;
        FieldInfo() fields = t.GetFields(BindingFlags.NonPublic |
                                         BindingFlags.Public |
        if (fields.Any())
            return true;
        return false;

Now, the method DoitNow is the core method here, it takes any object as a parameter, and uses projection to look through all the properties of it. If a field is a string field, we use the method sanitizeSensitiveString to sanitize the string. I a property is itself a object (I use the method isNested to determine this) I will call the method recursively on it. If a property is a List type, I look into the list and sanitize if it contains stirngs, and recurse if it contains complex objects.

I would like to get some tips on my Isnested method, am I using projection right? In general am I using projection In a way that makes sense to acces the fields and modify them?

Also, In order to be able to operate with many list types, I use the IList interface, however this has led me to using for-loops in a way that I find very un-elegant, can I replace some of my loops with some functional type function calls? I also use if (list.count != 0) to test if a list is empty, I just find this plain stupid.

Any other optimizations are welcomed!

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Providing two methods single + collection vs. only the collection

Edited Question based on the comments and great feedback (thanks)

I have a REST controller exposing two GET endpoints.

  • GetById – taking a single id (string)
  • GetById – taking multiple id’s (a collection of type string)

The only thing the controller does is call the service/domain layer which also exposes the GetById method.
Both of these methods are part of the public interaface of the service layer.

The question is in regards to design, is it a good choice to force the client to create a collection from a single string e. g. new {myId}, or should the public API support both of these methods?

Original Question

I am currently facing the following situation.
I have a REST Controller which accepts a single string (an id). This id is then passed to the underlying service layer which has a method also taking one string (the id).

Now I have the requirement to also accept multiple id’s. The REST controller must accept multiple id’s, however my question is, should the service layer provide now only one method taking multiple id’s (List/Enumerable) or should the method be overloaded with both, a single string and a collection?

Thank you!