operation

问题 I have a list of (mongodb) Embedded Documents within one Document and I am interested in adding a new embedded document to the list of the existing ones. As far as I have researched, I can use $addToSet, what I can't figure out is how does MongoDB decide if the new document already exists in the list of embedded documents or if it's a new one, i.e. how does MongoDB decide if 2 embedded documents are equal? p.s. the embedded documents I have are not just values, they are quite complex

问题 Follwing another post: I would like to know if OCL allows the following. Imagine the following UML diagram. How to use ocl to model: "a person can drinkWater() only if he is from country name 'ABCD'" AND if the population of the country is >= 1000000" Of course, the example is purely fictive. ================ ================ | Person | | Country | |--------------| |--------------| |- name |------------------|- id | |- age | |- name | |--------------| |- population | |+ drinkWater()| ========

问题 If I have a data.frame like this: X1 X2 1 1 A 2 2 A 3 3 B 4 4 B 5 5 A 6 6 A 7 7 B 8 8 B 9 9 A 10 10 A My goal is to define a set of data.frame as: y1<-data[1:2,] y2<-data[3:4,] y3<-data[5:6,] ##...etc. by a loop. Therefore, ideally I would like to use (for instance) a for loop for (i in 1:5){ y_i <- data[2*i:2*(i+1), ] } However, I cannot figure out how to define a subsequent set of data.frame such as y_i. Is there any method able to do this? Thanks in advance. 回答1: You can use assign . It

问题 I have two lists ListA and ListB as follow: ListA=['1','1','2','2','2','3','4','4','5','5','5','5'] ListB=['1','5'] I am trying to come up with List C which has the same length as List A but replace the numbers in the List A with 'X' if the number is in the List B .The result i am expecting: ListC=['X','X','2','2','2','3','4','4','X','X','X','X'] FYI, length of ListB will always less than the length of ListA and ListB will not hold any numbers that is not in List A . I have tried like this:

问题 In R, I often times need to do the same operation for a group of variables. As an example, on my environment I currently have the following of data frames: df_model1 df_model2 df_model3 df_model4 df_model5 and I have another data frame called df_obs . What I need to do is to merge each of the df-model* data frame to df_obs . What I usually do is something like this: new_df_model1 <- merge(df_obs, df_model1, all=TRUE) new_df_model2 <- merge(df_obs, df_model2, all=TRUE) ... and so on, which is

问题 I built a model in Tensorflow and I'm trying to convert it into a TensorFlow Estimator. Here is an example of what I have: train_op = tf.train.AdamOptimizer(learning_rate=lr).minimize(cost) saver = tf.train.Saver() init = tf.global_variables_initializer() assign_Wvh = pretrained_rsm.temporal_assignment(params['W']) with tf.Session() as sess: sess.run(init) for epoch in range(epochs): start = time.time() _ = sess.run(train_op, feed_dict={x: input}) print("%i. elapsed time: %0.2f" % (epoch,

问题 Can somebody please explain me why the code below behaves like it does? (It's Python in command line on Windows7 x64) >>>2.22 + 0.22 2.44000000000000004 >>>(222+22)/100 2.44 回答1: Floating point operations are limited in percision, and in python the limitations are well documented. You can read about it here 回答2: All floating point math is like this and is based on the IEEE standard. 回答3: Floating point oprations are known to cause errors. http://en.wikipedia.org/wiki/IEEE_floating_point Use

问题 Suppose that I use another SDK (which I do not have control of) with an API that imports 1 file asynchronously, and calls a completion callback on completion. The following is an example API. func importFile(filePath: String, completion: () -> Void) I need to import 10 files (one by one) using this API, but I need it to be cancellable, e.g. after Files 1,2,3 has been successfully imported, while File 4 is being imported, I want to be able to cancel the whole set of operations (import of the

问题 I have tried both 1) smthng = any (select id from exmplTable) 2) smthng in (select id from exmplTable) and I am getting the same results for my data. Is there any difference for the two expresions ? 回答1: No, in these variants are same: You can see - the execution plans are same too: postgres=# explain select * from foo1 where id in (select id from foo2); ┌──────────────────────────────────────────────────────────────────┐ │ QUERY PLAN │ ╞═══════════════════════════════════════════════════════