C++ functions: invalid initialization of non-const reference of type
What does `invalid initialization of non-const reference` mean?
Help Text not showing on I have a table inside of a pageblocksection and then inside of that I have an  that I am trying to utilize the default help text for but it's not showing up.  &lt;apex:pageBlockSection columns="1"&gt;   &lt;apex:outputPanel&gt;     &lt;table&gt; width="100%"&gt;       &lt;tr&gt;         &lt;td&gt;           &lt;apex:pageBlockSectionItem helpText="test text"&gt;             &lt;apex:inputCheckbox value="{!searchBySKU}" /&gt;             &lt;apex:outputLabel value="Search for this SKU or text in the SKU name" /&gt;           &lt;/apex:pageBlockSectionItem&gt;         &lt;/td&gt;       &lt;/tr&gt;     &lt;/table&gt;   &lt;/apex:outputPanel&gt; &lt;/apex:pageBlockSection&gt;   Any ideas why this doesn't work as I expect?  EDIT:  So, I just did some more testing and it creates the text if it's a direct child of the pageBlockSection. Is there any way to get around this restriction without going the fully custom route to do so? How to edit Parameters for an Object after it is created? Determining bare earth DEM from unclassified LAS file? I have data in LAS format with RGB values created from aerial photogrammetry using a UAV. I am  trying to find a solution to extract the bare earth DEM from the point cloud.   I have tried SAGA, Fusion, MCC-LIDAR, but it is seems they need the LAS file to be already classified (which it naturally isn't). Can anyone point me in the right direction with a brief explanation of the process?   Generally, I would need to process about 100 mill points at a time (can tile them if needed). Is there a function or method to give the last day of a month? For example if the date is 27 feb 2013, the last date should be 28 feb 2013 , it become 29 if its a leap year. if the date was 2 jan then it should return 31 Jan.  If there is no function then any ideas on how we can get this?  Thanks Probability for roots of quadratic equation to be real, with coefficients being dice rolls. I really need help with this question.     The coefficients $a,b,c$ of the quadratic equation $ax^2+bx+c=0$ are determined by throwing $3$ dice and reading off the value shown on the uppermost face of each die, so that the first die gives $a$, the second $b$ and and third $c$. Find the probabilities that the roots the equations are real, complex and equal.   I was thinking about using the fundamental formula but i'm not sure how to go about doing it. Help would be greatly appreciated. This is about a step in a derivation of the expression for the relativistic Doppler effect.  Consider a source receding from an observer at a velocity $v$ along the line joining the two. Light is emitted at frequency $f_s$ and wavelength $\lambda_s$. The frequency $f_0$ and wavelength $\lambda_0$ received by the observer will be different.  Some textbooks now argue that the wavelength received by the observer is given by $\lambda_0=(c+u)T_0$, where $T_0$ is the time period of the wave in the observers frame. The argument given is that the successive "crests" will be an extra distance $uT_0$ apart due to movement of the source. Upon relativistically transforming the time period in the source frame to the observer frame, the correct result $f_0=f_s\sqrt{\frac{c-u}{c+u}}$ is obtained.  But the argument for the wavelength seems reminiscent of the classical Doppler effect for sound. Is it really applicable here through this argument? And is there a way to show the same result for $\lambda_0$ mathematically? Lasso regression feature selection I have been reading many articles on LASSO regression, and everyone claims that LASSO address multicollinearity showing contour plots of cost function touching the corner of the diamond(x1+x2). In the first place, I didn't understand how does this phenomenon translate to addressing multicollinearity when there are many groups of correlated variables in the data.  Verbatim from one of the research paper: "• If there are grouped variables (highly correlated between each other) LASSO tends to select one variable from each group ignoring the others". Why were the people of Rhun and Harad allied with Sauron?  Did they join him out of fear, or did Sauron say he would give them something if they joined him?  I know the men of Dunland were angry at Rohan; did Rhun and Harad have something against Gondor? Self-Contained Proof that $\sum\limits_{n=1}^{\infty} \frac1{n^p}$ Converges for $p > 1$ To prove the convergence of the p-series   $$\sum_{n=1}^{\infty} \frac1{n^p}$$  for $p &gt; 1$, one typically appeals to either the Integral Test or the Cauchy Condensation Test.  I am wondering if there is a self-contained proof that this series converges which does not rely on either test.    I suspect that any proof would have to use the ideas behind one of these two tests. Need help to understand Maximum Likelihood Estimation for multivariate normal distribution? In maximum likelihood estimation for the parameter, mean $\mu$ of multivariate normal distribution, I end up with the following result:  $\mu_{MLE} = \dfrac{1}{n}\sum_{i=1}^n x_i$  The way I understand the above equation is the following way below, but I am wondering if the above equation means the following equation:  $\mu_{MLE} = \begin{bmatrix}\mu_1\\\mu_2\\\vdots\\\mu_n\end{bmatrix} = \begin{bmatrix}\dfrac{1}{n}\sum_{i=1}^n x_1\\\dfrac{1}{n}\sum_{i=1}^n x_2\\\vdots\\\dfrac{1}{n}\sum_{i=1}^n x_i\end{bmatrix} = \begin{bmatrix}E(X_1)\\E(X_2)\\\vdots\\E(X_n)\end{bmatrix} = \begin{bmatrix}\bar{X_1} \\ \bar{X_2} \\ \vdots \\ \bar{X_n}\end{bmatrix}$   And also Maximum Likelhood Estimation for $\Sigma$, I have ended up with the following equation:  $\Sigma_{MLE} = \dfrac{1}{n}\sum_{i=1}^n(x_i-\mu)(x_i-\mu)^T = \begin{bmatrix}Var(\sigma_{11}) &amp; Cov(\sigma_{12}) &amp; \dots &amp; Cov(\sigma_{1n}) \\ Cov(\sigma_{21}) &amp; Var(\sigma_{22}) &amp; \dots &amp; Cov(\sigma_{2n}) \\ {}&amp; \vdots&amp;  \\ Cov(\sigma_{n1}) &amp; Cov(\sigma_{n2}) &amp; \dots &amp; Var(\sigma_{nn})  \end{bmatrix}$  Somehow, I got the equation following some algebraic steps, but I can't see how this part, $\dfrac{1}{n}\sum_{i=1}^n(x_i-\mu)(x_i-\mu)^T$, works and produces the covariance matrix. Hope to hear some explanations. Read from location on console C# Repeating an equation including its content and number When should I use # and = in ASP.NET controls? How can I efficiently recover a permanently deleted folder at once? Ship an application with a database Word for Party *Steward*? Is there a word that describes a person who is usually not too drunk and takes care of the rest of the folks at a party?  Typically, they're the ones who drag the sloshed ones back to beds, clean up the house and generally maintain a bit of sanity. Finding the Dimension of a Matrix Polynomial: $W$ = { $p(B)$ : $p$ is a polynomial with real coefficients} Let $W = \{ p(B) : p \text{ is a polynomial with real coefficients}\}$, where $$B= \begin{pmatrix} 0 &amp; 1 &amp; 0\\  0 &amp; 0 &amp; 1\\  1 &amp; 0 &amp; 0 \end{pmatrix}$$  Which of the following possibilities presents the tightest bounds on the dimension $d$ of the vector space $W$?     $4 ≤ d ≤ 6$    $6 ≤ d ≤ 9$    $3 ≤ d ≤ 8$    $3 ≤ d ≤ 4$ How to get the result of OnPostExecute() to main activity because AsyncTask is a separate class? GDAL HDF4 Driver on Linux System I'm running code that works with MODIS HDF4 datasets on a Debian Linux distribution.  I am also running this code on a Windows machine.  On both the Windows and the Linux machines, I have the most recent GDAL version (gdal 1.11.1, np19py27_1), however on the Linux machine, GDAL doesn't seem to recognize HDF4 Drivers... it won't load or process any of the HDF4 datasets that are easily processed on the Windows machine (unfortunately this machine doesn't have enough space to run the full code).  Has anyone else encountered this problem?  Do I need to install an additional module on the Linux system? Suppose that $X$ and $Y$ are chosen randomly and independently according to the uniform distribution from $(0,1)$. Define $$ Z=\frac{\max(X,Y)}{\min(X,Y)}.$$ Compute the probability distribution function of $Z$. Can anyone give me some hints on how to proceed? I can only note that $\mathbb{P}[Z\geq 1]=1$ and $$F_Z(t)= \mathbb{P}[Z \leq t]=\mathbb{P}[X\leq Y, Y\leq tX]+\mathbb{P}[Y \leq X, x\leq tY]$$