How to increase the frequency of data collection per second and record the data upto 4 decimal point

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The default is to print 2 decimal places when printing the float data type. If you want to print more places use the second (optional) argument.

Serial.print(float, places);
Serial.print(float, 5);  // will print 5 decimal places.

See the reference for the print function.

An optional second parameter ... For floating point numbers, this parameter specifies the number of decimal places to use. For example-