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Summarizing multiple columns with dplyr? [duplicate]
I'm struggling a bit with the dplyr-syntax. I have a data frame with different variables and one grouping variable. Now I want to calculate the mean for each column within each group, using dplyr in R.
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Type converting slices of interfaces
I'm curious why Go does't implicitly convert []T to []interface{} when it will implicitly convert T to interface{} . Is there something non-trivial about this conversion that I'm missing?
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Setting unique Constraint with fluent API?
I'm trying to build an EF Entity with Code First, and an EntityTypeConfiguration using fluent API. creating primary keys is easy but not so with a Unique Constraint. I was seeing old posts that suggested executing native SQL commands for this, but that seem to defeat the purpose. is this possible ...
Get ID of last inserted document in a mongoDB w/ Java driver
Is there an easy way to get the ID (ObjectID) of the last inserted document of a mongoDB instance using the Java driver?
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What's the meaning of interface{}?
I'm new to interfaces and trying to do SOAP request by github
6 Answers
6
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C语言结构体里的成员数组和指针 - c++1y / stl - 清泛IT社区，为创新赋能！
...把代码copy过去编译和调试，我把代码列在下面：#include <stdio.h>
struct str{
int len;
char s[0];
};
struct foo {
struct str *a;
};
int main(int argc, char** argv) {
struct foo f={0};
if (f.a->s) {
&n...
How to convert list of key-value tuples into dictionary?
I have a list that looks like:
7 Answers
7
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When do you use varargs in Java?
I'm afraid of varargs. I don't know what to use them for.
8 Answers
8
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What is the proper way to check for null values?
I love the null-coalescing operator because it makes it easy to assign a default value for nullable types.
10 Answers
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printf format specifiers for uint32_t and size_t
I have the following
4 Answers
4
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