A computer-implemented method of conducting directed evolution of proteins to identify protein variants of desired activity, the method comprising: (a) obtaining sequence and activity data for each of a plurality of protein variants; (b) generating a multiplicative sequence-activity model from the sequence and activity data, in which multiple non-interaction multiplicative terms are combined by multiplication, wherein the sequence-activity model comprises: a dependent variable representing the activity of a protein variant and a product of multiple non-interaction multiplicative terms wherein the multiple non-interaction multiplicative terms are combined by multiplication, wherein each of the non-interaction multiplicative terms comprises a product of a coefficient and an independent variable, wherein: (i) the coefficient represents the contribution to activity of a single defined amino acid at a single defined position in the protein sequence, and (ii) the independent variable represents the presence or absence of the single defined amino acid at the single defined position in the protein sequence, and wherein each of the non-interaction multiplicative terms represents only the single defined amino acid at the single defined position in the protein sequence; and wherein the multiplicative sequence-activity model predicts activity as a function of sequence information; and (c) using the multiplicative sequence-activity model to guide a round of directed evolution, by using the multiplicative sequence-activity model to predict activity from sequence information, wherein protein variants of desired activity are identified through the directed evolution. (a) obtaining sequence and activity data for each of a plurality of protein variants; (b) generating a multiplicative sequence-activity model from the sequence and activity data, in which multiple non-interaction multiplicative terms are combined by multiplication, wherein the sequence-activity model comprises: a dependent variable representing the activity of a protein variant and a product of multiple non-interaction multiplicative terms wherein the multiple non-interaction multiplicative terms are combined by multiplication, wherein each of the non-interaction multiplicative terms comprises a product of a coefficient and an independent variable, wherein: (i) the coefficient represents the contribution to activity of a single defined amino acid at a single defined position in the protein sequence, and (ii) the independent variable represents the presence or absence of the single defined amino acid at the single defined position in the protein sequence, and wherein each of the non-interaction multiplicative terms represents only the single defined amino acid at the single defined position in the protein sequence; and wherein the multiplicative sequence-activity model predicts activity as a function of sequence information; and wherein the sequence-activity model comprises: a dependent variable representing the activity of a protein variant and a product of multiple non-interaction multiplicative terms wherein the multiple non-interaction multiplicative terms are combined by multiplication, wherein each of the non-interaction multiplicative terms comprises a product of a coefficient and an independent variable, wherein: (i) the coefficient represents the contribution to activity of a single defined amino acid at a single defined position in the protein sequence, and (ii) the independent variable represents the presence or absence of the single defined amino acid at the single defined position in the protein sequence, and wherein each of the non-interaction multiplicative terms represents only the single defined amino acid at the single defined position in the protein sequence; a dependent variable representing the activity of a protein variant and a product of multiple non-interaction multiplicative terms wherein the multiple non-interaction multiplicative terms are combined by multiplication, wherein each of the non-interaction multiplicative terms comprises a product of a coefficient and an independent variable, wherein: (i) the coefficient represents the contribution to activity of a single defined amino acid at a single defined position in the protein sequence, and (ii) the independent variable represents the presence or absence of the single defined amino acid at the single defined position in the protein sequence, (i) the coefficient represents the contribution to activity of a single defined amino acid at a single defined position in the protein sequence, and (ii) the independent variable represents the presence or absence of the single defined amino acid at the single defined position in the protein sequence, and wherein each of the non-interaction multiplicative terms represents only the single defined amino acid at the single defined position in the protein sequence; and wherein the multiplicative sequence-activity model predicts activity as a function of sequence information; and (c) using the multiplicative sequence-activity model to guide a round of directed evolution, by using the multiplicative sequence-activity model to predict activity from sequence information, wherein protein variants of desired activity are identified through the directed evolution.