Hot answers tagged

4

You did not provide SQL product so I will give one example. You need a random function from your DBMS. For example oracle provides dbms_random.value, SQL server NEWID or RAND(). MySql provides RAND(). Assume that you have a table named DATA which holds your 500 records. WITH TEMP ( SELECT ROW_NUMBER() AS ROW_ID , NEWID() as RANDOM_VALUE,D.* ...


4

If you only need relative scoring you can just use $X\hat{\beta}$ from the Cox model, otherwise you need to consider the underlying survival curve and state what you want to predict (probability, mean, quantile, etc.). The R rms package facilitates much of this by providing code generators Function, Quantile, Mean and for R functions created by Function (...


2

Open Ofice serves as a freeware alternative to Microsoft Office. It has a database program called Base that is analogous to Access.


2

What you are trying to estimate in economics is referred to as the cross-price elasticity of demand, how demand for a good $Y$ changes in response to a change in the price $p_x$ of good $X$. Several points to keep in mind: To estimate a demand curve, you need to use shifts in the supply curve. For example, if we were trying to estimate how demand for apple ...


1

SQL is a query language used by many different databases. “Big data“ is a broad, catch-all, term for many different, pretty diverse, technologies. It’s like asking if it is better to learn Spanish, or “Asian languages”. Moreover, many of the query languages that can be used with big data databases are based on SQL, do you need to learn it first. I don’t ...


1

Welcome to the site, @Nick, and good luck with your job application. I will wade in regarding your forth question. Whenever data are collected from scratch, which seems to be the case here, you have to understand first why the data are collected. Let's say in this case the data are collected to help the company predict which customers are likely to opt ...


1

This would be a classification problem. You can use binary classifier labeling male and female. I'm assuming the question number would be the feature and the answers the observations. There are many classification algorithms however you should perform some kind of exploratory analysis before you attempt to classify to get a better understanding of the ...


1

The most convenient data layout for analysis will likely depend on the model you're using. Presumably you haven't already chosen a model, so for the meantime, collect the data into whatever format is convenient for collection, keeping in mind principles of good database design such as fourth normal form. I'm imagining something like Discount ID | Item ID | ...


1

I would suggest an alternative if you insist on doing simple univariate regression... Regress on prediction errors. ie predict using one variable, now do univariate regression of error on next variable... This is equivalent to multiple regression but not so numerically well behaved. There is another alternative Elements of statistical learning, 3.2.3 ...


1

You should probably start by familiarizing yourself with the High Performance Computing Task View. The final answer could depend on several things that you have not told us. If this is a simple linear model then you could simply construct a select statement in SQL to pass to the database that multiplies each variable by its slope and adds the results (...


1

This should be a good start for ya, but you need work on your understanding of the statistical modeling and pre-processing of data. FYI: This will error out at the end because I did not handle the index so you can go ahead and correct that. Also, SequenceVar this will become your factor that is inputted into the model, also I do not know what your data ...


1

A sequential algorithm using conditional probabilities can also be used. To demonstrate a simple case, suppose you want to sample 1 item out of 4. Generate a uniform[0,1] random number $U_1$. If $U_1 < {1 \over 4}$, select the first element. If not, generate $U_2$. If $U_2 < {1 \over 3}$, select the second element. If not, generate $U_3$. If $U_3 < {...


1

Although the FLOOR answer is probably nicer, you can do this with a vlookup. The first column of the lookup table (shown below) is the lower bound of each of your bins. Then you enter a formula to make the labels in the second column (formula shown, and result of the formula in the third column -- obviously you'd only have two columns.) Note the last two ...


Only top voted, non community-wiki answers of a minimum length are eligible