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Missing value support for integers in SPSS #251

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Missing value support for integers in SPSS#251
@gorcha

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@gorcha
gorcha
opened on Aug 4, 2021

Another one from haven! 🙂
From tidyverse/haven#596.

Currently missing value support for SPSS is limited to doubles and strings because of an explicit type check in the functions that write out the missing values info:

ReadStat/src/spss/readstat_sav_write.c

Lines 244 to 259 in a8e6705

static readstat_error_t sav_n_missing_values(int *out_n_missing_values, readstat_variable_t *r_variable) {
int n_missing_values = 0;
if (r_variable->type == READSTAT_TYPE_DOUBLE) {
n_missing_values = sav_n_missing_double_values(r_variable);
} else if (readstat_variable_get_storage_width(r_variable) <= 8) {
n_missing_values = sav_n_missing_string_values(r_variable);
}
if (abs(n_missing_values) > 3) {
return READSTAT_ERROR_TOO_MANY_MISSING_VALUE_DEFINITIONS;
}
if (out_n_missing_values)
*out_n_missing_values = n_missing_values;
return READSTAT_OK;
}

ReadStat/src/spss/readstat_sav_write.c

Lines 346 to 353 in a8e6705

static readstat_error_t sav_emit_variable_missing_values(readstat_writer_t *writer, readstat_variable_t *r_variable) {
if (r_variable->type == READSTAT_TYPE_DOUBLE) {
return sav_emit_variable_missing_double_values(writer, r_variable);
} else if (readstat_variable_get_storage_width(r_variable) <= 8) {
return sav_emit_variable_missing_string_values(writer, r_variable);
}
return READSTAT_OK;
}

It seems like it should be OK to just use the double methods for all non-string values (since integers and 32 bit floats are all converted to doubles in SPSS output anyway) - it probably just needs a change to the conditional logic in these functions and maybe a couple of additional readstat_add_missing_* functions in here to deal with other types:
https://github.com/WizardMac/ReadStat/blob/a8e6705453f0e610a698a4d98b3dfa3087cf4b28/src/readstat_variable.c

I can chuck together a PR if you're happy with this approach?

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