indexing

Error: unsupported use of matrix or array for column indexing

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I have a list of variables name “comorbid_names”. And I want to select people who have those comorbidities in “comorbidities”. However, I want to select the variable names if they are true. For example patient 1 has “chd” only, therefore only that will be displayed as TRUE comorbid_names [1] “chd” “heart_failure” “stroke”[4] “hypertension” “diabetes” “copd”[7] … Read more

How to map with index in Ruby?

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If you’re using ruby 1.8.7 or 1.9, you can use the fact that iterator methods like each_with_index, when called without a block, return an Enumerator object, which you can call Enumerable methods like map on. So you can do: In 1.8.6 you can do:

What does ‘index 0 is out of bounds for axis 0 with size 0’ mean?

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In numpy, index and dimension numbering starts with 0. So axis 0 means the 1st dimension. Also in numpy a dimension can have length (size) 0. The simplest case is: I also get it if x = np.zeros((0,5), int), a 2d array with 0 rows, and 5 columns. So someplace in your code you are creating an array with a size … Read more

Get first row value of a given column

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To select the ith row, use iloc: To select the ith value in the Btime column you could use: There is a difference between df_test[‘Btime’].iloc[0] (recommended) and df_test.iloc[0][‘Btime’]: DataFrames store data in column-based blocks (where each block has a single dtype). If you select by column first, a view can be returned (which is quicker than returning a copy) and the original dtype is preserved. In … Read more

Pop index out of range

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To get the final value of a list pop’ed, you can do it this way: Keep in mind that pop removes the item, and the list changes length after the pop. Use negative numbers to index from the end of a list that may be changing in size, or just use pop() with no arguments for the … Read more

Python Pandas: Get index of rows which column matches certain value

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df.iloc[i] returns the ith row of df. i does not refer to the index label, i is a 0-based index. In contrast, the attribute index returns actual index labels, not numeric row-indices: or equivalently, You can see the difference quite clearly by playing with a DataFrame with a non-default index that does not equal to the row’s numerical position: If you want to use the index, … Read more

How to index into a dictionary?

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Dictionaries are unordered in Python versions up to and including Python 3.6. If you do not care about the order of the entries and want to access the keys or values by index anyway, you can create a list of keys for a dictionary d using keys = list(d), and then access keys in the list by index keys[i], … Read more