nan

问题 I have "None" and "nan" strings scattered in my dataframe. Is there a way to replace all of those with empty string "" or nan so they do not show up when I export the dataframe as excel sheet? Simplified Example: Note: nan in col4 are not strings ID col1 col2 col3 col4 1 Apple nan nan nan 2 None orange None nan 3 None nan banana nan The output should be like this after removing all the "None" and "nan" strings when we replaced them by empty strings "" : ID col1 col2 col3 col4 1 Apple nan 2

问题 Disclaimer: No, I didn't find any obvious answer, contrary to what I expected! When looking for code examples wrt. the arithmetic mean, the first several examples I can turn up via Google seem to be defined such that the empty sequence generates a mean value of 0.0 . (eg. here and here ...) Looking at Wikipedia however, the Arithmetic mean is defined such that an empty sequence would yield 0.0 / 0 -- A = 1/n ∑[i=1 -> n](a[i]) -- so, possibly, that is NaN in the general case. So if I write a

问题 My understanding of the rules of IEEE-754 floating-point comparisons is that all comparison operators except != will return false if either or both arguments are NaN, while the != operator will return true. I can easily reproduce this behavior with a simple standalone test: for (int ii = 0; ii < 4; ++ii) { float a = (ii & 1) != 0 ? NAN : 1.0f; float b = (ii & 2) != 0 ? NAN : 2.0f; #define TEST(OP) printf("%4.1f %2s %4.1f => %s\n", a, #OP, b, a OP b ? "true" : "false"); TEST(<) TEST(>) TEST(<=

问题 My understanding of the rules of IEEE-754 floating-point comparisons is that all comparison operators except != will return false if either or both arguments are NaN, while the != operator will return true. I can easily reproduce this behavior with a simple standalone test: for (int ii = 0; ii < 4; ++ii) { float a = (ii & 1) != 0 ? NAN : 1.0f; float b = (ii & 2) != 0 ? NAN : 2.0f; #define TEST(OP) printf("%4.1f %2s %4.1f => %s\n", a, #OP, b, a OP b ? "true" : "false"); TEST(<) TEST(>) TEST(<=

问题 My understanding of the rules of IEEE-754 floating-point comparisons is that all comparison operators except != will return false if either or both arguments are NaN, while the != operator will return true. I can easily reproduce this behavior with a simple standalone test: for (int ii = 0; ii < 4; ++ii) { float a = (ii & 1) != 0 ? NAN : 1.0f; float b = (ii & 2) != 0 ? NAN : 2.0f; #define TEST(OP) printf("%4.1f %2s %4.1f => %s\n", a, #OP, b, a OP b ? "true" : "false"); TEST(<) TEST(>) TEST(<=

问题 My understanding of the rules of IEEE-754 floating-point comparisons is that all comparison operators except != will return false if either or both arguments are NaN, while the != operator will return true. I can easily reproduce this behavior with a simple standalone test: for (int ii = 0; ii < 4; ++ii) { float a = (ii & 1) != 0 ? NAN : 1.0f; float b = (ii & 2) != 0 ? NAN : 2.0f; #define TEST(OP) printf("%4.1f %2s %4.1f => %s\n", a, #OP, b, a OP b ? "true" : "false"); TEST(<) TEST(>) TEST(<=

问题 My understanding of the rules of IEEE-754 floating-point comparisons is that all comparison operators except != will return false if either or both arguments are NaN, while the != operator will return true. I can easily reproduce this behavior with a simple standalone test: for (int ii = 0; ii < 4; ++ii) { float a = (ii & 1) != 0 ? NAN : 1.0f; float b = (ii & 2) != 0 ? NAN : 2.0f; #define TEST(OP) printf("%4.1f %2s %4.1f => %s\n", a, #OP, b, a OP b ? "true" : "false"); TEST(<) TEST(>) TEST(<=

问题 I have a function that returns a double value. In some cases the result is zero, and this results should be handled in the caller routing accordingly. I was wondering what is the proper way of returning zero (NaN, false, etc!) in place of double value number: double foo(){ if (some_conditions) { return result_of_calculations; } else { // Which of the following is better? return std::numeric_limits<double>::quiet_NaN(); // (1) return 0; // (2) return false; // (3) return (int) 0; // (4) } }

问题 I read that NaNs are problematic, but the following causes an actual corruption of my data, rather than an error. Is this a bug? Have I missed something basic in the documentation? I would like the second command to give an error or to give the same response as the first command: ipdb> df year PRuid QC data 18 2007 nonQC 0 8.014261 19 2008 nonQC 0 7.859152 20 2010 nonQC 0 7.468260 21 1985 10 NaN 0.861403 22 1985 11 NaN 0.878531 23 1985 12 NaN 0.842704 24 1985 13 NaN 0.785877 25 1985 24 1 0

问题 I have this dataframe which includes nans: Date 0 7.0 1 8.0 2 9.0 3 10.0 4 11.0 5 12.0 6 1.0 7 2.0 8 3.0 9 4.0 10 5.0 11 6.0 ... 90 NaN 91 NaN The Date values are the month number, and I know that on the index 90 it is a 1 but I want to fill the other NaNs with 2, 3 etc until 12 then goes back to 1, 2 and so on. Lets say it just like in Excel, when you want to fill a column, you put the first values then select them and slide all the way and it fills automatically. Any ideas ? Thanks ! 回答1: